Solve 3x + 9 = −3

The solution of 3x + 9 = −3 is x = -4.

3x + 9 = -3\ \Rightarrow\ x = -4

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

LaTeX source of the formulas on this page

\[ 3x + 9 = -3\ \Rightarrow\ x = -4 \]
\[ 3x + 9 = -3 \]
\[ 3x + 9 - 9 = -3 - 9 \ \Rightarrow\ 3x = -12 \]
\[ \frac{3x}{3} = \frac{-12}{3} \ \Rightarrow\ x = -4 \]
\[ 3\cdot(-4) + 9 = -12 + 9 = -3 \checkmark \]

Trying values of x in 3x + 9 = −3

x	3x + 9	Equals -3?
-6	-9	no
-5	-6	no
-4	-3	yes
-3	0	no
-2	3	no

Questions

What is x in 3x + 9 = −3?

The solution of 3x + 9 = −3 is x = -4.

How do you solve 3x + 9 = −3?

Subtract 9 from both sides to get 3x = -12, then divide both sides by 3 to get x = -4.

How do I check the answer?

Replace x by -4: 3(-4) + 9 = -3, which is -3.

Solve 3x + 9 = −3

How to work it out

Trying values of x in 3x + 9 = −3

Questions

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