Solve 10x − 9 = −99

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

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

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

LaTeX source of the formulas on this page

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

Trying values of x in 10x − 9 = −99

x	10x − 9	Equals -99?
-11	-119	no
-10	-109	no
-9	-99	yes
-8	-89	no
-7	-79	no

Questions

What is x in 10x − 9 = −99?

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

How do you solve 10x − 9 = −99?

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

How do I check the answer?

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

Solve 10x − 9 = −99

How to work it out

Trying values of x in 10x − 9 = −99

Questions

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