Solve 12x + 9 = −15

The solution of 12x + 9 = −15 is x = -2.

12x + 9 = -15\ \Rightarrow\ x = -2

Explain it step by step in chat Make a short video of it

The lines y = 12x + 9 and y = -15 meet at x = -2. 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.
$12x + 9 = -15$
2
Subtract 9 from both sides:
$12x + 9 - 9 = -15 - 9 \ \Rightarrow\ 12x = -24$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-24}{12} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$12\cdot(-2) + 9 = -24 + 9 = -15 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 9 = -15\ \Rightarrow\ x = -2 \]
\[ 12x + 9 = -15 \]
\[ 12x + 9 - 9 = -15 - 9 \ \Rightarrow\ 12x = -24 \]
\[ \frac{12x}{12} = \frac{-24}{12} \ \Rightarrow\ x = -2 \]
\[ 12\cdot(-2) + 9 = -24 + 9 = -15 \checkmark \]

Trying values of x in 12x + 9 = −15

x	12x + 9	Equals -15?
-4	-39	no
-3	-27	no
-2	-15	yes
-1	-3	no
0	9	no

Questions

What is x in 12x + 9 = −15?

The solution of 12x + 9 = −15 is x = -2.

How do you solve 12x + 9 = −15?

Subtract 9 from both sides to get 12x = -24, then divide both sides by 12 to get x = -2.

How do I check the answer?

Replace x by -2: 12(-2) + 9 = -15, which is -15.

Solve 12x + 9 = −15

How to work it out

Trying values of x in 12x + 9 = −15

Questions

Similar equations