Solve 9x + 15 = −75

The solution of 9x + 15 = −75 is x = -10.

9x + 15 = -75\ \Rightarrow\ x = -10

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The lines y = 9x + 15 and y = -75 meet at x = -10. 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 addition, then the multiplication.
$9x + 15 = -75$
2
Subtract 15 from both sides:
$9x + 15 - 15 = -75 - 15 \ \Rightarrow\ 9x = -90$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-90}{9} \ \Rightarrow\ x = -10$
4
Check: put x = -10 back into the equation.
$9\cdot(-10) + 15 = -90 + 15 = -75 \checkmark$

LaTeX source of the formulas on this page

\[ 9x + 15 = -75\ \Rightarrow\ x = -10 \]
\[ 9x + 15 = -75 \]
\[ 9x + 15 - 15 = -75 - 15 \ \Rightarrow\ 9x = -90 \]
\[ \frac{9x}{9} = \frac{-90}{9} \ \Rightarrow\ x = -10 \]
\[ 9\cdot(-10) + 15 = -90 + 15 = -75 \checkmark \]

Trying values of x in 9x + 15 = −75

x	9x + 15	Equals -75?
-12	-93	no
-11	-84	no
-10	-75	yes
-9	-66	no
-8	-57	no

Questions

What is x in 9x + 15 = −75?

The solution of 9x + 15 = −75 is x = -10.

How do you solve 9x + 15 = −75?

Subtract 15 from both sides to get 9x = -90, then divide both sides by 9 to get x = -10.

How do I check the answer?

Replace x by -10: 9(-10) + 15 = -75, which is -75.

Solve 9x + 15 = −75

How to work it out

Trying values of x in 9x + 15 = −75

Questions

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