Solve 10x + 9 = −71

The solution of 10x + 9 = −71 is x = -8.

10x + 9 = -71\ \Rightarrow\ x = -8

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The lines y = 10x + 9 and y = -71 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 addition, then the multiplication.
$10x + 9 = -71$
2
Subtract 9 from both sides:
$10x + 9 - 9 = -71 - 9 \ \Rightarrow\ 10x = -80$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{-80}{10} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$10\cdot(-8) + 9 = -80 + 9 = -71 \checkmark$

LaTeX source of the formulas on this page

\[ 10x + 9 = -71\ \Rightarrow\ x = -8 \]
\[ 10x + 9 = -71 \]
\[ 10x + 9 - 9 = -71 - 9 \ \Rightarrow\ 10x = -80 \]
\[ \frac{10x}{10} = \frac{-80}{10} \ \Rightarrow\ x = -8 \]
\[ 10\cdot(-8) + 9 = -80 + 9 = -71 \checkmark \]

Trying values of x in 10x + 9 = −71

x	10x + 9	Equals -71?
-10	-91	no
-9	-81	no
-8	-71	yes
-7	-61	no
-6	-51	no

Questions

What is x in 10x + 9 = −71?

The solution of 10x + 9 = −71 is x = -8.

How do you solve 10x + 9 = −71?

Subtract 9 from 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) + 9 = -71, which is -71.

Solve 10x + 9 = −71

How to work it out

Trying values of x in 10x + 9 = −71

Questions

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