Solve 8x + 15 = −1

The solution of 8x + 15 = −1 is x = -2.

8x + 15 = -1\ \Rightarrow\ x = -2

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The lines y = 8x + 15 and y = -1 meet at x = -2. 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.
$8x + 15 = -1$
2
Subtract 15 from both sides:
$8x + 15 - 15 = -1 - 15 \ \Rightarrow\ 8x = -16$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{-16}{8} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$8\cdot(-2) + 15 = -16 + 15 = -1 \checkmark$

LaTeX source of the formulas on this page

\[ 8x + 15 = -1\ \Rightarrow\ x = -2 \]
\[ 8x + 15 = -1 \]
\[ 8x + 15 - 15 = -1 - 15 \ \Rightarrow\ 8x = -16 \]
\[ \frac{8x}{8} = \frac{-16}{8} \ \Rightarrow\ x = -2 \]
\[ 8\cdot(-2) + 15 = -16 + 15 = -1 \checkmark \]

Trying values of x in 8x + 15 = −1

x	8x + 15	Equals -1?
-4	-17	no
-3	-9	no
-2	-1	yes
-1	7	no
0	15	no

Questions

What is x in 8x + 15 = −1?

The solution of 8x + 15 = −1 is x = -2.

How do you solve 8x + 15 = −1?

Subtract 15 from both sides to get 8x = -16, then divide both sides by 8 to get x = -2.

How do I check the answer?

Replace x by -2: 8(-2) + 15 = -1, which is -1.

Solve 8x + 15 = −1

How to work it out

Trying values of x in 8x + 15 = −1

Questions

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