Solve 4x − 15 = −55

The solution of 4x − 15 = −55 is x = -10.

4x - 15 = -55\ \Rightarrow\ x = -10

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The lines y = 4x − 15 and y = -55 meet at x = -10. 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 subtraction, then the multiplication.
$4x - 15 = -55$
2
Add 15 to both sides:
$4x - 15 + 15 = -55 + 15 \ \Rightarrow\ 4x = -40$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{-40}{4} \ \Rightarrow\ x = -10$
4
Check: put x = -10 back into the equation.
$4\cdot(-10) - 15 = -40 - 15 = -55 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 15 = -55\ \Rightarrow\ x = -10 \]
\[ 4x - 15 = -55 \]
\[ 4x - 15 + 15 = -55 + 15 \ \Rightarrow\ 4x = -40 \]
\[ \frac{4x}{4} = \frac{-40}{4} \ \Rightarrow\ x = -10 \]
\[ 4\cdot(-10) - 15 = -40 - 15 = -55 \checkmark \]

Trying values of x in 4x − 15 = −55

x	4x − 15	Equals -55?
-12	-63	no
-11	-59	no
-10	-55	yes
-9	-51	no
-8	-47	no

Questions

What is x in 4x − 15 = −55?

The solution of 4x − 15 = −55 is x = -10.

How do you solve 4x − 15 = −55?

Add 15 to both sides to get 4x = -40, then divide both sides by 4 to get x = -10.

How do I check the answer?

Replace x by -10: 4(-10) − 15 = -55, which is -55.

Solve 4x − 15 = −55

How to work it out

Trying values of x in 4x − 15 = −55

Questions

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