Solve 8x − 15 = −79

The solution of 8x − 15 = −79 is x = -8.

8x - 15 = -79\ \Rightarrow\ x = -8

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The lines y = 8x − 15 and y = -79 meet at x = -8. 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.
$8x - 15 = -79$
2
Add 15 to both sides:
$8x - 15 + 15 = -79 + 15 \ \Rightarrow\ 8x = -64$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-64}{8} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$8\cdot(-8) - 15 = -64 - 15 = -79 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 15 = -79\ \Rightarrow\ x = -8 \]
\[ 8x - 15 = -79 \]
\[ 8x - 15 + 15 = -79 + 15 \ \Rightarrow\ 8x = -64 \]
\[ \frac{8x}{8} = \frac{-64}{8} \ \Rightarrow\ x = -8 \]
\[ 8\cdot(-8) - 15 = -64 - 15 = -79 \checkmark \]

Trying values of x in 8x − 15 = −79

x	8x − 15	Equals -79?
-10	-95	no
-9	-87	no
-8	-79	yes
-7	-71	no
-6	-63	no

Questions

What is x in 8x − 15 = −79?

The solution of 8x − 15 = −79 is x = -8.

How do you solve 8x − 15 = −79?

Add 15 to both sides to get 8x = -64, then divide both sides by 8 to get x = -8.

How do I check the answer?

Replace x by -8: 8(-8) − 15 = -79, which is -79.

Solve 8x − 15 = −79

How to work it out

Trying values of x in 8x − 15 = −79

Questions

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