Solve 7x − 9 = −72

The solution of 7x − 9 = −72 is x = -9.

7x - 9 = -72\ \Rightarrow\ x = -9

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The lines y = 7x − 9 and y = -72 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.
$7x - 9 = -72$
2
Add 9 to both sides:
$7x - 9 + 9 = -72 + 9 \ \Rightarrow\ 7x = -63$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-63}{7} \ \Rightarrow\ x = -9$
4
Check: put x = -9 back into the equation.
$7\cdot(-9) - 9 = -63 - 9 = -72 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 9 = -72\ \Rightarrow\ x = -9 \]
\[ 7x - 9 = -72 \]
\[ 7x - 9 + 9 = -72 + 9 \ \Rightarrow\ 7x = -63 \]
\[ \frac{7x}{7} = \frac{-63}{7} \ \Rightarrow\ x = -9 \]
\[ 7\cdot(-9) - 9 = -63 - 9 = -72 \checkmark \]

Trying values of x in 7x − 9 = −72

x	7x − 9	Equals -72?
-11	-86	no
-10	-79	no
-9	-72	yes
-8	-65	no
-7	-58	no

Questions

What is x in 7x − 9 = −72?

The solution of 7x − 9 = −72 is x = -9.

How do you solve 7x − 9 = −72?

Add 9 to both sides to get 7x = -63, then divide both sides by 7 to get x = -9.

How do I check the answer?

Replace x by -9: 7(-9) − 9 = -72, which is -72.

Solve 7x − 9 = −72

How to work it out

Trying values of x in 7x − 9 = −72

Questions

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