Solve 10x − 1 = −81

The solution of 10x − 1 = −81 is x = -8.

10x - 1 = -81\ \Rightarrow\ x = -8

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The lines y = 10x − 1 and y = -81 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.
$10x - 1 = -81$
2
Add 1 to both sides:
$10x - 1 + 1 = -81 + 1 \ \Rightarrow\ 10x = -80$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{-80}{10} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$10\cdot(-8) - 1 = -80 - 1 = -81 \checkmark$

LaTeX source of the formulas on this page

\[ 10x - 1 = -81\ \Rightarrow\ x = -8 \]
\[ 10x - 1 = -81 \]
\[ 10x - 1 + 1 = -81 + 1 \ \Rightarrow\ 10x = -80 \]
\[ \frac{10x}{10} = \frac{-80}{10} \ \Rightarrow\ x = -8 \]
\[ 10\cdot(-8) - 1 = -80 - 1 = -81 \checkmark \]

Trying values of x in 10x − 1 = −81

x	10x − 1	Equals -81?
-10	-101	no
-9	-91	no
-8	-81	yes
-7	-71	no
-6	-61	no

Questions

What is x in 10x − 1 = −81?

The solution of 10x − 1 = −81 is x = -8.

How do you solve 10x − 1 = −81?

Add 1 to both sides to get 10x = -80, then divide both sides by 10 to get x = -8.

How do I check the answer?

Replace x by -8: 10(-8) − 1 = -81, which is -81.

Solve 10x − 1 = −81

How to work it out

Trying values of x in 10x − 1 = −81

Questions

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