Solve 8x − 1 = 31

The solution of 8x − 1 = 31 is x = 4.

8x - 1 = 31\ \Rightarrow\ x = 4

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The lines y = 8x − 1 and y = 31 meet at x = 4. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$8x - 1 = 31$
2
Add 1 to both sides:
$8x - 1 + 1 = 31 + 1 \ \Rightarrow\ 8x = 32$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{32}{8} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$8\cdot4 - 1 = 32 - 1 = 31 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 1 = 31\ \Rightarrow\ x = 4 \]
\[ 8x - 1 = 31 \]
\[ 8x - 1 + 1 = 31 + 1 \ \Rightarrow\ 8x = 32 \]
\[ \frac{8x}{8} = \frac{32}{8} \ \Rightarrow\ x = 4 \]
\[ 8\cdot4 - 1 = 32 - 1 = 31 \checkmark \]

Trying values of x in 8x − 1 = 31

x	8x − 1	Equals 31?
2	15	no
3	23	no
4	31	yes
5	39	no
6	47	no

Questions

What is x in 8x − 1 = 31?

The solution of 8x − 1 = 31 is x = 4.

How do you solve 8x − 1 = 31?

Add 1 to both sides to get 8x = 32, then divide both sides by 8 to get x = 4.

How do I check the answer?

Replace x by 4: 8(4) − 1 = 31, which is 31.

Solve 8x − 1 = 31

How to work it out

Trying values of x in 8x − 1 = 31

Questions

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