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Fractional Powers

Are you aware that powers or exponents may not be whole numbers but fractions? Yes, exponents also exist as fractions and we would be discussing on them herein.

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Fractional Powers

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Are you aware that powers or exponents may not be whole numbers but fractions? Yes, exponents also exist as fractions and we would be discussing on them herein.

In this article, we will see what fractional powers are, what negative fractional powers are, their rules, and examples of application.

What are power of fraction exponents?

Fractional powers or fraction exponents are expressions which are being powered by fractions and are in the form xa/b .

We are more familiar with whole-number exponents in the form xa. Because x has been powered by a, it means x is multiplied by itself a times. However, when a fraction is a power or exponent, then, you may be finding the root of that expression. This implies that for a fractional exponent like x1/a, you are required to find the a root of x;

x1a=xa.

Solve for 2713.

Solution

2713=273=3×3×33=3

Solve for 3225

Solution

3225=(55)2 =(2×2×2×2×25)2 =22=4

What is the fractional power of a number in decimal form?

The power of a fraction in decimal form is an exponent which is a fraction that is expressed as a decimal. It occurs in the form;

xa.b,

where a and b are two digits and are separated by a decimal point. They can now be re-expressed to become;

a.b=ab10xa.b=xab10xab10=(x10)ab

Remember that a and b are the digits that form the decimal number a.b. For instance, considering the decimal number 3.2, where a and b would be 3 and 2, respectively. Let's see an example to clarify this better.

Solve for 320.2.

Solution

320.2

Recall that;

xa.b=xab10

Then;

a=0 and b=2320.2=320210=32210=3212510=3215=325

Recalling that 32=25, we then have

325=255=2

In conclusion,

320.2=2

What are negative fractional powers?

Negative fractional powers occur when an expression has been powered by a negative fraction. This appears in the form xa/b. When this occurs, the reciprocal of the expression is powered by the fraction. This then becomes

x-ab=1xab.

This is in line with the rule of negative exponents which states that

x-a=1xa.

The negative fractional powers is among the rules of fractional powers which shall be discussed below.

Rules of fractional powers

These rules when applied would enable you easily solve fractional exponents problems. However, before going to the rules note that fractional powers are defined by the form

x1a=xa

as well as

xab=(x1b)a x1b=xb(x1b)a=(xb)axab=(xb)a

With the knowledge of this definition, the following rules should be applied.

Rule 1: When the base for instance x is powered by a negative fraction for example -ab, find the b root of x and power by a, then find the reciprocal of the result.

x-ab=1(xb)a

x-ab=1xabxab=(xb)a 1xab=1(xb)ax-ab=1(xb)a

Solve 32-25.

Solution

By applying rule 1,

32-25=1(55)2 =1(2×2×2×2×25)2 =122=14

Rule 2: When the base is a fraction for instance xy, and is powered by a negative fraction for example -ab, find the b root of yx and power by a.

(xy)-ab=(yxb)a

(xy)-ab=1(xy)ab1(xy)ab=(yx)ab (yx)ab=(yxb)a (xy)-ab=(yxb)a

Solve (64125)-23

Solution

By applying rule 2,

(64125)-23=(125643)2 =(5×5×54×4×43)2=(54)2 =2516=1916

Rule 3: When the product of two or more fractional powers in this case, 1a and 1b, have the same base in this case x, then find the ab root of x and power by the sum of b and a.

x1a×x1b=(xab)(b+a)

x1a×x1b=x(1a+1b)x(1a+1b)=x(b+aab)x(b+aab)=(xab)(b+a)x1a×x1b=(xab)(b+a)

Solve 6412×6413.

Solution

By applying rule 3,

6412×6413=(64(2×3))(3+2) =(646)5=(2×2×2×2×2×26)5=25=32

Rule 4: When the product of two or more fractional powers in this case, ma and nb, have the same base in this case x, then find the ab root of x and power by the sum of bm and an.

xma×xnb=(xab)(bm+an)

xma×xnb=x(ma+nb)x(ma+nb)=x(bm+anab)x(bm+anab)=(xab)(bm+an)xma×xnb=(xab)(bm+an)

Solve 6432×6453

Solution

By applying rule 4,

6432×6453=(64(2×3))((3×3)+(2×5)) =(646)(9+10) =(646)14=(2×2×2×2×2×26)14=214=16384

Rule 5: When the quotient of two unit-fractional powers in this case, 1a and 1b, have the same base in this case x, then find the ab root of x and power by the difference of b and a.

x1a÷x1b=(xab)(b-a)

x1a÷x1b=x(1a-1b)x(1a-1b)=x(b-aab)x(b-aab)=(xab)(b-a)x1a÷x1b=(xab)(b-a)

Solve 6412÷6413

Solution

By applying rule 5,

6412÷6413=(64(2×3))(3-2) =(646)1=(2×2×2×2×2×26)1=21=2

Rule 6: When the quotient of two fractional powers in this case, ma and nb, have the same base in this case x, then find the ab root of x and power by the difference of bm and an.

xma÷xnb=(xab)(bm-an)

xma÷xnb=x(ma-nb)x(ma-nb)=x(bm-anab)x(bm-anab)=(xab)(bm-an)xma÷xnb=(xab)(bm-an)

Solve 6473÷6432.

Solution

By applying rule 6,

6473÷6432=(64(3×2))((2×7)-(3×3)) =(646)(14-9) =(646)5=(2×2×2×2×2×26)5=25=32

Rule 7: When the product of two fractional powers have different bases in this case x and y, but with the same powers in this case 1a, then find the a root of xy.

x1a×y1a=xya

x1a×y1a=(x×y)1a (x×y)1a=(xy)1a (xy)1a=xyax1a×y1a=xya

Solve 8114×1614.

Solution

By applying rule 7,

8114×1614=81×164=3×3×3×3×2×2×2×24=3×2=6

Rule 8: When the quotient of two fractional powers have different bases in this case x and y, but with the same powers in this case 1a, then find the a root of xy.

x1a÷y1a=xya

x1a÷y1a=(x÷y)1a (x÷y)1a=(xy)1a (xy)1a =xyax1a÷y1a=xya

Solve 8114÷1614.

Solution

By applying rule 8,

8114÷1614=81164=3×3×3×32×2×2×24=32=112

Solve the following;

a. (343y6)-23

b. 18012÷24512

c. 514×12514

Solution

a.

(343y6)-23

The first thing to do is to see if you can change the number to exponent form (indices).

Note that;

343=73

Therefore;

(343y6)-23=(73y6)-23

Recall that;

(xy)-ab==(yxb)a

Then;

(73y6)-23=(y673)23(y673)23=y(6×23)7(3×23)y(6×23)73×23=y(26×213)7(13×213)y(26×213)7(13×213)=(y2×2)7(1×2)(y2×2)7(1×2)=y472

b.

18012÷24512

Recall that;

x1a÷y1a=xya

Then;

18012÷24512=18024521802452=180245180245=180÷5245÷5180÷5245÷5=36493649=67

c.

514×12514

The first thing to do is to see if you can change the number to exponent form (indices).

Therefore;

125=53514×12514=514×(53)14 514×(53)14=514×5(3×14)514×5(3×14)=514×534

Recall that;

xma×xnb=(xab)(bm+an)

Then;

514×534=(5(4×4))((4×1)+(4×3)(5(4×4))((4×1)+(4×3)=(516)16 (516)16=(5116)16 (5116)16=5(116×16)5(116×16)=5151=5

or you could solve directly from this point;

514×5(3×14)=514×534514×534=5(14+34)5(14+34)=544544=5151=5

Binomial expansion for fractional powers

How is a binomial expansion for fractional powers done?

The binomial expansion for fractional powers is carried out simply by applying the formula

(1+a)n=1+na+n(n-1)2!a2+n(n-1)(n-2)3!a3+n(n-1)(n-2)(n-3)4!a4+...

where n is the power or exponent.

Solve for the first 4 terms of (8+2y)13.

Solution

(8+2y)13

Ensure you factorise or re-express the expression bearing the exponent to conform to the form;

(1+a).

So, your plan is to convert (8 + 2y) to (1 + y). To achieve that, factorise 8 + 2y by 8. You would have

(8+2y)==8(88+2y8)=8(1+y4)

Let

y4=a

Substitute into the equation

(8(1+a))13=813(1+a)13

Recalling that 813=2, we then have

813(1+a)13=2(1+a)13

Recall that

(1+a)n=1+na+n(n-1)2!a2+n(n-1)(n-2)3!a3+n(n-1)(n-2)(n-3)4!a4+...

Also, we are only interested in the first 4 terms, therefore;

2(1+a)13=2[1+13a+13(13-1)2!a2+13(13-1)(13-2)3!a3+...]=2[1+13a-292×1a2+10273×2×1a3+...]=2[1+13a-19a2+581a3+...]

Substitute the real value of a as;

a=y4

Therefore;

2[1+13a-19a2+581a3+...]=2[1+13(y4)-19(y4)2+581(y4)3+...]=2[1+y12-y2144+5y3324+...]=2+y6-y272+5y3162+...

And so

(8+2y)13=2+y6-y272+5y3162+...

Further examples in calculating fractional powers

Some more examples would give you a better understanding of fractional powers.

If the cube root of a number is squared and the result is 4. Find the number.

Solution

Let the unknown number be y. So the cube root of a number, y being square and resulting to 4 is expressed as (y13)2=4 .

Note that

x(ab)c=xacb

Then

(y13)2=4 (y13)2=y23y23=4

Take the reciprocal of the roots in both sides. The reciprocal of 23 is32, therefore;

y23=4(y23)32=432y(23×32)=432

Recall that

xab=(xb)a

So,

y(23×32)=y(23×32)=yy=432 y=(42)3 4=2y=23y=8

Fractional Powers - Key takeaways

  • Fractional powers or fraction exponents are expressions which are being powered by fractions and are in the form xa/b .
  • Negative fractional powers occurs when an expression has been powered by a negative fraction.
  • Fractional power rules when applied would enable you easily solve fractional exponents problems.
  • The binomial expansion for fractional powers is carried out simply by applying the formula;

    (1+a)n=1+na+n(n-1)2!a2+n(n-1)(n-2)3!a3+n(n-1)(n-2)(n-3)4!a4+...

Frequently Asked Questions about Fractional Powers

You integrate expressions with fractional powers by simply applying the rules of integral calculus.

You calculate fractional powers by applying the rules of fractional powers.

To solve numbers to the power of fractions, the denominator of the powered is the root while numerator is its normal exponent.

Binomial expansion with fractional powers is carried out by applying the formula of the binomial theorem.

You simplify algebraic fractions with powers by firstly converting them to indices if possible before solving with the powers.

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