Steply

Simplify 16^(3/4)

Step by step, with the reason for every step · Rational exponents · Algebra 1

Step by step

The question

Question: work out 16^(3/4).

16^(3/4)

A fraction power has two jobs.

The bottom number, 4, says which root: the 4th root.

The top number, 3, says which power.

a^(m/n) = (n√a)m

Careful!

The power is not times.

16 times 3/4 is a different number.

Careful: not 16^(3/4) = 16 × 34 ✗

1 Take the root

The bottom is 4: the 4th root of 16.

The top is 3: to the power 3.

We take the root first.

It keeps the numbers small.

= (4√16)3

The 4th root of 16 is 2, because 2 × 2 × 2 × 2 is 16.

2 × 2 × 2 × 2 = 16

We write 2 in place of the 4th root of 16.

= 23

2 Take the power

2 to the power 3 is 2 × 2 × 2.

That is 8.

2 × 2 × 2 = 8

So 16^(3/4) = 8.

= 8

3 Check

Let's check the other way: the power first, then the root.

16 to the power 3 is 4096.

Other order: 163 = 4096

The 4th root of 4096 is 8, because 8 × 8 × 8 × 8 is 4096.

We get 8 again.

But the numbers were bigger.

So root first is easier.

And the answer is right!

4√4096 = 8, 8 × 8 × 8 × 8 = 4096

Let's look back.

First: take the root.

Then: take the power.

Last: check.

Answer
= 8

Your turn

Try this one yourself, then check:

Work out 4^(3/2)
Show the answer
8

More from Rational exponents

The whole lesson: Rational exponents →