Solve 7x + 9 = −40

The solution of 7x + 9 = −40 is x = -7.

7x + 9 = -40\ \Rightarrow\ x = -7

Explain it step by step in chat Make a short video of it

The lines y = 7x + 9 and y = -40 meet at x = -7. 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.
$7x + 9 = -40$
2
Subtract 9 from both sides:
$7x + 9 - 9 = -40 - 9 \ \Rightarrow\ 7x = -49$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-49}{7} \ \Rightarrow\ x = -7$
4
Check: put x = -7 back into the equation.
$7\cdot(-7) + 9 = -49 + 9 = -40 \checkmark$

LaTeX source of the formulas on this page

\[ 7x + 9 = -40\ \Rightarrow\ x = -7 \]
\[ 7x + 9 = -40 \]
\[ 7x + 9 - 9 = -40 - 9 \ \Rightarrow\ 7x = -49 \]
\[ \frac{7x}{7} = \frac{-49}{7} \ \Rightarrow\ x = -7 \]
\[ 7\cdot(-7) + 9 = -49 + 9 = -40 \checkmark \]

Trying values of x in 7x + 9 = −40

x	7x + 9	Equals -40?
-9	-54	no
-8	-47	no
-7	-40	yes
-6	-33	no
-5	-26	no

Questions

What is x in 7x + 9 = −40?

The solution of 7x + 9 = −40 is x = -7.

How do you solve 7x + 9 = −40?

Subtract 9 from both sides to get 7x = -49, then divide both sides by 7 to get x = -7.

How do I check the answer?

Replace x by -7: 7(-7) + 9 = -40, which is -40.

Solve 7x + 9 = −40

How to work it out

Trying values of x in 7x + 9 = −40

Questions

Similar equations