Solve 10x + 15 = −75

The solution of 10x + 15 = −75 is x = -9.

10x + 15 = -75\ \Rightarrow\ x = -9

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The lines y = 10x + 15 and y = -75 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 addition, then the multiplication.
$10x + 15 = -75$
2
Subtract 15 from both sides:
$10x + 15 - 15 = -75 - 15 \ \Rightarrow\ 10x = -90$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{-90}{10} \ \Rightarrow\ x = -9$
4
Check: put x = -9 back into the equation.
$10\cdot(-9) + 15 = -90 + 15 = -75 \checkmark$

LaTeX source of the formulas on this page

\[ 10x + 15 = -75\ \Rightarrow\ x = -9 \]
\[ 10x + 15 = -75 \]
\[ 10x + 15 - 15 = -75 - 15 \ \Rightarrow\ 10x = -90 \]
\[ \frac{10x}{10} = \frac{-90}{10} \ \Rightarrow\ x = -9 \]
\[ 10\cdot(-9) + 15 = -90 + 15 = -75 \checkmark \]

Trying values of x in 10x + 15 = −75

x	10x + 15	Equals -75?
-11	-95	no
-10	-85	no
-9	-75	yes
-8	-65	no
-7	-55	no

Questions

What is x in 10x + 15 = −75?

The solution of 10x + 15 = −75 is x = -9.

How do you solve 10x + 15 = −75?

Subtract 15 from 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) + 15 = -75, which is -75.

Solve 10x + 15 = −75

How to work it out

Trying values of x in 10x + 15 = −75

Questions

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