Linear Expressions

Did you know that a number of real-life problems that contain unknown quantities could be modeled into mathematical statements to help solve them easily? In this article, we are going to discuss linear expressions, what they look like, and how to solve them.

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Table of contents

    What are linear expressions?

    Linear expressions are algebraic expressions containing constants and variables raised to the power of 1.

    For example, x + 4 - 2 is a linear expression because the variable here x is also a representation of x1. The moment there is such a thing as x2, it ceases to be a linear expression.

    Here are some more examples of linear expressions:

    1. 3x + y

    2. x + 2 - 6

    3. 34x

    What are variables, terms, and coefficients?

    Variables are the letter components of expressions. These are what differentiate arithmetic operations from expressions. Terms are the components of expressions that are separated by addition or subtraction, and coefficients are the numerical factors multiplying variables.

    For example, if we were given the expression6xy +(3), x and y could be identified as the variable components of the expression. The number 6 is identified as the coefficient of the term6xy. The number3is called a constant. The identified terms here are6xy and-3.

    We can take a few examples and categorize their components under either variables, coefficients, or terms.

    1. 45y + 14x - 3
    2. 2 - 4x
    3. 12 + xy
    x and y45 and 14-345y, 14x and -3
    x-422 and -4x
    x and y1 (though it's not shown, this is technically the coefficient of xy)1212 and xy
    Variables are what differentiate expressions from arithmetic operations

    Writing linear expressions

    Writing linear expressions involves writing the mathematical expressions out of word problems. There are mostly keywords that help out with what kind of operation to be done when writing an expression from a word problem.

    KeywordsAdded toPlusSum ofIncreased byTotal ofMore thanSubtracted fromMinusLess thanDifferenceDecreased byFewer thanTake awayMultiplied byTimesProduct ofTimes ofDivided byQuotient of
    We can go ahead to take examples of how this is done.

    Write the phrase below as an expression.

    14 more than a numberx


    This phrase suggests that we add. However, we need to be careful about the positioning. 14 more thanx means 14 is being added to a certain numberx.

    14 + x

    Write the phrase below as an expression.

    The difference of 2 and 3 times a numberx.


    We should look out for our keywords here, "difference" and "times". "Difference" means we will be subtracting. So we are going to subtract 3 times a number from 2.

    2 - 3x

    Simplifying linear expressions

    Simplifying linear expressions is the process of writing linear expressions in their most compact and simplest forms such that the value of the original expression is maintained.

    There are steps to follow when one wants to simplify expressions, and these are;

    • Eliminate the brackets by multiplying the factors if there are any.

    • Add and subtract the like terms.

    Simplify the linear expression.

    3x + 2 (x 4)


    Here, we will first operate on the brackets by multiplying the factor (outside the bracket) by what is in the brackets.


    We will add like terms.


    This means that the simplified form ofid="2671931" role="math" 3x + 2 (x 4) isid="2671932" role="math" 5x-8, and they possess the same value.

    Linear equations are also forms of linear expressions. Linear expressions are the name that covers linear equations and linear inequalities.

    Linear equations

    Linear equations are linear expressions that possess an equal sign. They are the equations with degree 1. For example, id="2671933" role="math" x+4 = 2. Linear equations are in standard form as

    ax + by = c

    whereid="2671946" role="math" a andid="2671935" role="math" bare coefficients

    x andyare variables.

    c is constant.

    However, x is also known as the x-intercept, whilst they is also the y-intercept. When a linear equation possesses one variable, the standard form is written as;

    ax + b = 0

    where x is a variable

    a is a coefficient

    b is a constant.

    Graphing linear equations

    As mentioned earlier that linear equations are graphed in a straight line, it is important to know that with a one-variable equation, linear equation lines are parallel to the x-axis because only the x value is taken into consideration. Lines graphed from two-variable equations are placed where the equations demand that it is placed, although still straight. We can go ahead and take an example of a linear equation in two variables.

    Plot the graph for the line id="2671968" role="math" x - 2y = 2.


    First, we will convert the equation into the form id="2671969" role="math" y = mx + b.

    By this, we can know what the y-intercept is too.

    This means we will make y the subject of the equation.

    x - 2y = 2

    -2y = 2 - x

    -2y-2 = 2-2- x-2

    y = x2 - 1

    Now we can explore the y values for different values of x as this is also considered as the linear function.

    So take x = 0

    This means we will substitute x into the equation to find y.

    y = 02-1

    y = -1

    Take id="2671970" role="math" x = 2

    y = 22 - 1

    y = 0

    Take x = 4

    y = 42-1

    y = 1

    What this actually means is that when

    x = 0, y = -1

    x = 2, y = 0

    x = 4, y = 1

    and so on.

    We will now draw our graph and indicate the x and y-axis are.

    After which we will plot the points we have and draw a line through them.

    Linear expressions, Graphing, StudySmarterGraph of line x - 2y = 2

    Solving Linear equations

    Solving linear equations involve finding the values for either x and/or y in a given equation. Equations could be in a one-variable form or a two-variable form. In the one variable form,x, representing the variable is made the subject and solved algebraically.

    With the two-variable form, it requires another equation to be able to give you absolute values. Remember in the example where we solved for the values ofy, whenx = 0, y = -1. And when x = 2, y = 0. This means that as long as x was different, y was going to be different too. We can take an example into solving them below.

    Solve the linear equation

    3y-x=710y +3x = -2


    We will solve this by substitution. Makexthe subject of the equation in the first equation.

    3y -7 = x

    Substitute it into the second equation

    10y + 3(3y 7) = -2

    10y + 9y 21 = -2

    19y = -2 + 21

    19y = 19

    y = 1

    Now we can substitute this value of y into one of the two equations. We will choose the first equation.

    3(1) - x =7

    3 - x = 7

    -x = 7 - 3

    -x-1 = 4-1

    x = -4

    This means that with this equation, when x = -4, y = 1

    This can be evaluated to see if the statement is true

    We can substitute the values of each variable found into any of the equations. Let us take the second equation.

    10y +3x = -2

    x = -4

    y = 1

    10(1) - 3(-4) = -2

    10 - 12 = -2

    -2 = -2

    This means that our equation is true if we sayy = 1when x = - 4.

    Linear Inequalities

    These are expressions used to make comparisons between two numbers using the inequalities symbols such as <, >, . Below, we will look at what the symbols are and when they are used.

    Symbol nameSymbolExample
    Not equaly 7
    Less than<2x < 4
    Greater than>2 > y
    Less than or equal to1 + 4x 9
    Greater than or equal to3y 9 - 4x

    Solving Linear Inequalities

    The primary aim of solving inequalities is to find the range of values that satisfy the inequality. This mathematically means that the variable should be left on one side of the inequality. Most of the things done to equations are done to inequalities too. Things like the application of the golden rule. The difference here is that some operative activities can change the signs in question such that < becomes >, > becomes <, ≤ becomes ≥, and ≥ becomes ≤. These activities are;

    • Multiply (or divide) both sides by a negative number.

    • Swapping sides of the inequality.

    Simplify the linear inequality4x - 3 21 and solve forx.


    You first need to add 3 to each side,

    4x - 3 + 3 21 + 3

    4x 24

    Then divide each side by 4.

    4x4 244

    The inequality symbol remains in the same direction.

    x 6

    Any number 6 or greater is a solution to the inequality4x - 3 21.

    Linear Expressions - Key takeaways

    • Linear expressions are those statements that each term that is either a constant or a variable raised to the first power.
    • Linear equations are the linear expressions that possess the equal sign.
    • Linear inequalities are those linear expressions that compare two values using the <, >, ≥, ≤, and ≠ symbols.
    Frequently Asked Questions about Linear Expressions

    What is a linear expression?

    Linear expressions are those statements that each term is either a constant or a variable raised to the first power. 

    How to add linear expression?

    Group the like terms, and add them such that terms with the same variables are added, and constants are also added.

    How do you factor linear expressions?

    Step 1: Group the first two terms together and then the last two terms together. 

    Step 2: Factor out a GCF from each separate binomial. 

    Step 3: Factor out the common binomial. Note that if we multiply our answer out, we do get the original polynomial. 

    However, linear factors appear in the form of ax + b and cannot be factored further. Each linear factor represents a different line that, when combined with other linear factors, result in different types of functions with increasingly complex graphical representations.

    What is the formula for linear expression?

    There are no particular formulas for solving linear equations. However, linear expressions in one variable are expressed as;

     ax + b, where, a ≠ 0 and x is the variable.

    Linear expressions in two variables are expressed as;

    ax + by  + c

    What are the rules for solving linear expression?

    The addition/subtraction rule and the multiplication/division rule.

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