Solve 8x − 15 = −39

The solution of 8x − 15 = −39 is x = -3.

8x - 15 = -39\ \Rightarrow\ x = -3

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The lines y = 8x − 15 and y = -39 meet at x = -3. 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.
$8x - 15 = -39$
2
Add 15 to both sides:
$8x - 15 + 15 = -39 + 15 \ \Rightarrow\ 8x = -24$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-24}{8} \ \Rightarrow\ x = -3$
4
Check: put x = -3 back into the equation.
$8\cdot(-3) - 15 = -24 - 15 = -39 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 15 = -39\ \Rightarrow\ x = -3 \]
\[ 8x - 15 = -39 \]
\[ 8x - 15 + 15 = -39 + 15 \ \Rightarrow\ 8x = -24 \]
\[ \frac{8x}{8} = \frac{-24}{8} \ \Rightarrow\ x = -3 \]
\[ 8\cdot(-3) - 15 = -24 - 15 = -39 \checkmark \]

Trying values of x in 8x − 15 = −39

x	8x − 15	Equals -39?
-5	-55	no
-4	-47	no
-3	-39	yes
-2	-31	no
-1	-23	no

Questions

What is x in 8x − 15 = −39?

The solution of 8x − 15 = −39 is x = -3.

How do you solve 8x − 15 = −39?

Add 15 to both sides to get 8x = -24, then divide both sides by 8 to get x = -3.

How do I check the answer?

Replace x by -3: 8(-3) − 15 = -39, which is -39.

Solve 8x − 15 = −39

How to work it out

Trying values of x in 8x − 15 = −39

Questions

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