Solve 12x + 9 = −3

The solution of 12x + 9 = −3 is x = -1.

12x + 9 = -3\ \Rightarrow\ x = -1

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The lines y = 12x + 9 and y = -3 meet at x = -1. 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.
$12x + 9 = -3$
2
Subtract 9 from both sides:
$12x + 9 - 9 = -3 - 9 \ \Rightarrow\ 12x = -12$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-12}{12} \ \Rightarrow\ x = -1$
4
Check: put x = -1 back into the equation.
$12\cdot(-1) + 9 = -12 + 9 = -3 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 9 = -3\ \Rightarrow\ x = -1 \]
\[ 12x + 9 = -3 \]
\[ 12x + 9 - 9 = -3 - 9 \ \Rightarrow\ 12x = -12 \]
\[ \frac{12x}{12} = \frac{-12}{12} \ \Rightarrow\ x = -1 \]
\[ 12\cdot(-1) + 9 = -12 + 9 = -3 \checkmark \]

Trying values of x in 12x + 9 = −3

x	12x + 9	Equals -3?
-3	-27	no
-2	-15	no
-1	-3	yes
0	9	no
1	21	no

Questions

What is x in 12x + 9 = −3?

The solution of 12x + 9 = −3 is x = -1.

How do you solve 12x + 9 = −3?

Subtract 9 from both sides to get 12x = -12, then divide both sides by 12 to get x = -1.

How do I check the answer?

Replace x by -1: 12(-1) + 9 = -3, which is -3.

Solve 12x + 9 = −3

How to work it out

Trying values of x in 12x + 9 = −3

Questions

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