Solve 8x + 15 = −25

The solution of 8x + 15 = −25 is x = -5.

8x + 15 = -25\ \Rightarrow\ x = -5

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The lines y = 8x + 15 and y = -25 meet at x = -5. 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.
$8x + 15 = -25$
2
Subtract 15 from both sides:
$8x + 15 - 15 = -25 - 15 \ \Rightarrow\ 8x = -40$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-40}{8} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$8\cdot(-5) + 15 = -40 + 15 = -25 \checkmark$

LaTeX source of the formulas on this page

\[ 8x + 15 = -25\ \Rightarrow\ x = -5 \]
\[ 8x + 15 = -25 \]
\[ 8x + 15 - 15 = -25 - 15 \ \Rightarrow\ 8x = -40 \]
\[ \frac{8x}{8} = \frac{-40}{8} \ \Rightarrow\ x = -5 \]
\[ 8\cdot(-5) + 15 = -40 + 15 = -25 \checkmark \]

Trying values of x in 8x + 15 = −25

x	8x + 15	Equals -25?
-7	-41	no
-6	-33	no
-5	-25	yes
-4	-17	no
-3	-9	no

Questions

What is x in 8x + 15 = −25?

The solution of 8x + 15 = −25 is x = -5.

How do you solve 8x + 15 = −25?

Subtract 15 from both sides to get 8x = -40, then divide both sides by 8 to get x = -5.

How do I check the answer?

Replace x by -5: 8(-5) + 15 = -25, which is -25.

Solve 8x + 15 = −25

How to work it out

Trying values of x in 8x + 15 = −25

Questions

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