Solve 8x − 15 = −31

The solution of 8x − 15 = −31 is x = -2.

8x - 15 = -31\ \Rightarrow\ x = -2

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The lines y = 8x − 15 and y = -31 meet at x = -2. 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.
$8x - 15 = -31$
2
Add 15 to both sides:
$8x - 15 + 15 = -31 + 15 \ \Rightarrow\ 8x = -16$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-16}{8} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$8\cdot(-2) - 15 = -16 - 15 = -31 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 15 = -31\ \Rightarrow\ x = -2 \]
\[ 8x - 15 = -31 \]
\[ 8x - 15 + 15 = -31 + 15 \ \Rightarrow\ 8x = -16 \]
\[ \frac{8x}{8} = \frac{-16}{8} \ \Rightarrow\ x = -2 \]
\[ 8\cdot(-2) - 15 = -16 - 15 = -31 \checkmark \]

Trying values of x in 8x − 15 = −31

x	8x − 15	Equals -31?
-4	-47	no
-3	-39	no
-2	-31	yes
-1	-23	no
0	-15	no

Questions

What is x in 8x − 15 = −31?

The solution of 8x − 15 = −31 is x = -2.

How do you solve 8x − 15 = −31?

Add 15 to both sides to get 8x = -16, then divide both sides by 8 to get x = -2.

How do I check the answer?

Replace x by -2: 8(-2) − 15 = -31, which is -31.

Solve 8x − 15 = −31

How to work it out

Trying values of x in 8x − 15 = −31

Questions

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