Solve 8x − 13 = −21

The solution of 8x − 13 = −21 is x = -1.

8x - 13 = -21\ \Rightarrow\ x = -1

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The lines y = 8x − 13 and y = -21 meet at x = -1. 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.
$8x - 13 = -21$
2
Add 13 to both sides:
$8x - 13 + 13 = -21 + 13 \ \Rightarrow\ 8x = -8$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-8}{8} \ \Rightarrow\ x = -1$
4
Check: put x = -1 back into the equation.
$8\cdot(-1) - 13 = -8 - 13 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 13 = -21\ \Rightarrow\ x = -1 \]
\[ 8x - 13 = -21 \]
\[ 8x - 13 + 13 = -21 + 13 \ \Rightarrow\ 8x = -8 \]
\[ \frac{8x}{8} = \frac{-8}{8} \ \Rightarrow\ x = -1 \]
\[ 8\cdot(-1) - 13 = -8 - 13 = -21 \checkmark \]

Trying values of x in 8x − 13 = −21

x	8x − 13	Equals -21?
-3	-37	no
-2	-29	no
-1	-21	yes
0	-13	no
1	-5	no

Questions

What is x in 8x − 13 = −21?

The solution of 8x − 13 = −21 is x = -1.

How do you solve 8x − 13 = −21?

Add 13 to both sides to get 8x = -8, then divide both sides by 8 to get x = -1.

How do I check the answer?

Replace x by -1: 8(-1) − 13 = -21, which is -21.

Solve 8x − 13 = −21

How to work it out

Trying values of x in 8x − 13 = −21

Questions

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