Steply

Solve x^3 = 50

Step by step, with the reason for every step · Solve x² = 49 and x³ = 27 · Foundations

Step by step

The question

Question: solve x³ = 50.

x3 = 50

x³ means x times x times x.

We want just x.

x³ = x × x × x

1 Cube root of both sides

The cube root asks: which number, times itself three times, makes this?

∛27 = ? → ? × ? × ? = 27

The cubes: 1 times 1 times 1 is 1.

2 times 2 times 2 is 8.

3 times 3 times 3 is 27.

4 times 4 times 4 is 64.

1³ = 1, 2³ = 8, 3³ = 27, 4³ = 64

x is the cube root of 50.

x = 3√50

50 is not a cube.

It is between 27 and 64.

So the answer is between 3 and 4.

3³ = 27 < 50 < 64 = 4³

A calculator gives 3.684, and so on.

x = 3.684…

To the nearest tenth, x is about 3.7.

x ≈ 3.7

Careful!

A cube has one answer, not two.

A negative number cubed is negative.

Not like x² = 49.

Careful: not x ≈ ±3.7 ✗

2 Check

Let's check: 3.7 times 3.7 times 3.7 is 50.653.

Very close to 50: we rounded.

So the answer is right!

3.7 × 3.7 × 3.7 = 50.653 ≈ 50

Let's look back.

First: cube root of both sides.

Last: check.

Answer
Careful: not x ≈ ±3.7 ✗

Your turn

Try this one yourself, then check:

Solve x3 = 30
Show the answer
x ≈ 3.1

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