Solve 9x − 9 = −99

The solution of 9x − 9 = −99 is x = -10.

9x - 9 = -99\ \Rightarrow\ x = -10

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The lines y = 9x − 9 and y = -99 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.
$9x - 9 = -99$
2
Add 9 to both sides:
$9x - 9 + 9 = -99 + 9 \ \Rightarrow\ 9x = -90$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-90}{9} \ \Rightarrow\ x = -10$
4
Check: put x = -10 back into the equation.
$9\cdot(-10) - 9 = -90 - 9 = -99 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 9 = -99\ \Rightarrow\ x = -10 \]
\[ 9x - 9 = -99 \]
\[ 9x - 9 + 9 = -99 + 9 \ \Rightarrow\ 9x = -90 \]
\[ \frac{9x}{9} = \frac{-90}{9} \ \Rightarrow\ x = -10 \]
\[ 9\cdot(-10) - 9 = -90 - 9 = -99 \checkmark \]

Trying values of x in 9x − 9 = −99

x	9x − 9	Equals -99?
-12	-117	no
-11	-108	no
-10	-99	yes
-9	-90	no
-8	-81	no

Questions

What is x in 9x − 9 = −99?

The solution of 9x − 9 = −99 is x = -10.

How do you solve 9x − 9 = −99?

Add 9 to both sides to get 9x = -90, then divide both sides by 9 to get x = -10.

How do I check the answer?

Replace x by -10: 9(-10) − 9 = -99, which is -99.

Solve 9x − 9 = −99

How to work it out

Trying values of x in 9x − 9 = −99

Questions

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