Solve 9x + 15 = −30

The solution of 9x + 15 = −30 is x = -5.

9x + 15 = -30\ \Rightarrow\ x = -5

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The lines y = 9x + 15 and y = -30 meet at x = -5. 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.
$9x + 15 = -30$
2
Subtract 15 from both sides:
$9x + 15 - 15 = -30 - 15 \ \Rightarrow\ 9x = -45$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-45}{9} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$9\cdot(-5) + 15 = -45 + 15 = -30 \checkmark$

LaTeX source of the formulas on this page

\[ 9x + 15 = -30\ \Rightarrow\ x = -5 \]
\[ 9x + 15 = -30 \]
\[ 9x + 15 - 15 = -30 - 15 \ \Rightarrow\ 9x = -45 \]
\[ \frac{9x}{9} = \frac{-45}{9} \ \Rightarrow\ x = -5 \]
\[ 9\cdot(-5) + 15 = -45 + 15 = -30 \checkmark \]

Trying values of x in 9x + 15 = −30

x	9x + 15	Equals -30?
-7	-48	no
-6	-39	no
-5	-30	yes
-4	-21	no
-3	-12	no

Questions

What is x in 9x + 15 = −30?

The solution of 9x + 15 = −30 is x = -5.

How do you solve 9x + 15 = −30?

Subtract 15 from both sides to get 9x = -45, then divide both sides by 9 to get x = -5.

How do I check the answer?

Replace x by -5: 9(-5) + 15 = -30, which is -30.

Solve 9x + 15 = −30

How to work it out

Trying values of x in 9x + 15 = −30

Questions

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