Solve 9x + 15 = −39

The solution of 9x + 15 = −39 is x = -6.

9x + 15 = -39\ \Rightarrow\ x = -6

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The lines y = 9x + 15 and y = -39 meet at x = -6. 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.
$9x + 15 = -39$
2
Subtract 15 from both sides:
$9x + 15 - 15 = -39 - 15 \ \Rightarrow\ 9x = -54$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-54}{9} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$9\cdot(-6) + 15 = -54 + 15 = -39 \checkmark$

LaTeX source of the formulas on this page

\[ 9x + 15 = -39\ \Rightarrow\ x = -6 \]
\[ 9x + 15 = -39 \]
\[ 9x + 15 - 15 = -39 - 15 \ \Rightarrow\ 9x = -54 \]
\[ \frac{9x}{9} = \frac{-54}{9} \ \Rightarrow\ x = -6 \]
\[ 9\cdot(-6) + 15 = -54 + 15 = -39 \checkmark \]

Trying values of x in 9x + 15 = −39

x	9x + 15	Equals -39?
-8	-57	no
-7	-48	no
-6	-39	yes
-5	-30	no
-4	-21	no

Questions

What is x in 9x + 15 = −39?

The solution of 9x + 15 = −39 is x = -6.

How do you solve 9x + 15 = −39?

Subtract 15 from both sides to get 9x = -54, then divide both sides by 9 to get x = -6.

How do I check the answer?

Replace x by -6: 9(-6) + 15 = -39, which is -39.

Solve 9x + 15 = −39

How to work it out

Trying values of x in 9x + 15 = −39

Questions

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