Solve 4x + 9 = −15

The solution of 4x + 9 = −15 is x = -6.

4x + 9 = -15\ \Rightarrow\ x = -6

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The lines y = 4x + 9 and y = -15 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.
$4x + 9 = -15$
2
Subtract 9 from both sides:
$4x + 9 - 9 = -15 - 9 \ \Rightarrow\ 4x = -24$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{-24}{4} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$4\cdot(-6) + 9 = -24 + 9 = -15 \checkmark$

LaTeX source of the formulas on this page

\[ 4x + 9 = -15\ \Rightarrow\ x = -6 \]
\[ 4x + 9 = -15 \]
\[ 4x + 9 - 9 = -15 - 9 \ \Rightarrow\ 4x = -24 \]
\[ \frac{4x}{4} = \frac{-24}{4} \ \Rightarrow\ x = -6 \]
\[ 4\cdot(-6) + 9 = -24 + 9 = -15 \checkmark \]

Trying values of x in 4x + 9 = −15

x	4x + 9	Equals -15?
-8	-23	no
-7	-19	no
-6	-15	yes
-5	-11	no
-4	-7	no

Questions

What is x in 4x + 9 = −15?

The solution of 4x + 9 = −15 is x = -6.

How do you solve 4x + 9 = −15?

Subtract 9 from both sides to get 4x = -24, then divide both sides by 4 to get x = -6.

How do I check the answer?

Replace x by -6: 4(-6) + 9 = -15, which is -15.

Solve 4x + 9 = −15

How to work it out

Trying values of x in 4x + 9 = −15

Questions

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