Solve 9x − 9 = −90

The solution of 9x − 9 = −90 is x = -9.

9x - 9 = -90\ \Rightarrow\ x = -9

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The lines y = 9x − 9 and y = -90 meet at x = -9. 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.
$9x - 9 = -90$
2
Add 9 to both sides:
$9x - 9 + 9 = -90 + 9 \ \Rightarrow\ 9x = -81$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-81}{9} \ \Rightarrow\ x = -9$
4
Check: put x = -9 back into the equation.
$9\cdot(-9) - 9 = -81 - 9 = -90 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 9 = -90\ \Rightarrow\ x = -9 \]
\[ 9x - 9 = -90 \]
\[ 9x - 9 + 9 = -90 + 9 \ \Rightarrow\ 9x = -81 \]
\[ \frac{9x}{9} = \frac{-81}{9} \ \Rightarrow\ x = -9 \]
\[ 9\cdot(-9) - 9 = -81 - 9 = -90 \checkmark \]

Trying values of x in 9x − 9 = −90

x	9x − 9	Equals -90?
-11	-108	no
-10	-99	no
-9	-90	yes
-8	-81	no
-7	-72	no

Questions

What is x in 9x − 9 = −90?

The solution of 9x − 9 = −90 is x = -9.

How do you solve 9x − 9 = −90?

Add 9 to both sides to get 9x = -81, then divide both sides by 9 to get x = -9.

How do I check the answer?

Replace x by -9: 9(-9) − 9 = -90, which is -90.

Solve 9x − 9 = −90

How to work it out

Trying values of x in 9x − 9 = −90

Questions

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