Solve 4x − 8 = −40

The solution of 4x − 8 = −40 is x = -8.

4x - 8 = -40\ \Rightarrow\ x = -8

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The lines y = 4x − 8 and y = -40 meet at x = -8. 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.
$4x - 8 = -40$
2
Add 8 to both sides:
$4x - 8 + 8 = -40 + 8 \ \Rightarrow\ 4x = -32$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{-32}{4} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$4\cdot(-8) - 8 = -32 - 8 = -40 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 8 = -40\ \Rightarrow\ x = -8 \]
\[ 4x - 8 = -40 \]
\[ 4x - 8 + 8 = -40 + 8 \ \Rightarrow\ 4x = -32 \]
\[ \frac{4x}{4} = \frac{-32}{4} \ \Rightarrow\ x = -8 \]
\[ 4\cdot(-8) - 8 = -32 - 8 = -40 \checkmark \]

Trying values of x in 4x − 8 = −40

x	4x − 8	Equals -40?
-10	-48	no
-9	-44	no
-8	-40	yes
-7	-36	no
-6	-32	no

Questions

What is x in 4x − 8 = −40?

The solution of 4x − 8 = −40 is x = -8.

How do you solve 4x − 8 = −40?

Add 8 to both sides to get 4x = -32, then divide both sides by 4 to get x = -8.

How do I check the answer?

Replace x by -8: 4(-8) − 8 = -40, which is -40.

Solve 4x − 8 = −40

How to work it out

Trying values of x in 4x − 8 = −40

Questions

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