Solve 9x + 15 = −12

The solution of 9x + 15 = −12 is x = -3.

9x + 15 = -12\ \Rightarrow\ x = -3

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The lines y = 9x + 15 and y = -12 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 addition, then the multiplication.
$9x + 15 = -12$
2
Subtract 15 from both sides:
$9x + 15 - 15 = -12 - 15 \ \Rightarrow\ 9x = -27$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-27}{9} \ \Rightarrow\ x = -3$
4
Check: put x = -3 back into the equation.
$9\cdot(-3) + 15 = -27 + 15 = -12 \checkmark$

LaTeX source of the formulas on this page

\[ 9x + 15 = -12\ \Rightarrow\ x = -3 \]
\[ 9x + 15 = -12 \]
\[ 9x + 15 - 15 = -12 - 15 \ \Rightarrow\ 9x = -27 \]
\[ \frac{9x}{9} = \frac{-27}{9} \ \Rightarrow\ x = -3 \]
\[ 9\cdot(-3) + 15 = -27 + 15 = -12 \checkmark \]

Trying values of x in 9x + 15 = −12

x	9x + 15	Equals -12?
-5	-30	no
-4	-21	no
-3	-12	yes
-2	-3	no
-1	6	no

Questions

What is x in 9x + 15 = −12?

The solution of 9x + 15 = −12 is x = -3.

How do you solve 9x + 15 = −12?

Subtract 15 from both sides to get 9x = -27, then divide both sides by 9 to get x = -3.

How do I check the answer?

Replace x by -3: 9(-3) + 15 = -12, which is -12.

Solve 9x + 15 = −12

How to work it out

Trying values of x in 9x + 15 = −12

Questions

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