Solve 5x + 9 = −21

The solution of 5x + 9 = −21 is x = -6.

5x + 9 = -21\ \Rightarrow\ x = -6

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The lines y = 5x + 9 and y = -21 meet at x = -6. 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.
$5x + 9 = -21$
2
Subtract 9 from both sides:
$5x + 9 - 9 = -21 - 9 \ \Rightarrow\ 5x = -30$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-30}{5} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$5\cdot(-6) + 9 = -30 + 9 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 5x + 9 = -21\ \Rightarrow\ x = -6 \]
\[ 5x + 9 = -21 \]
\[ 5x + 9 - 9 = -21 - 9 \ \Rightarrow\ 5x = -30 \]
\[ \frac{5x}{5} = \frac{-30}{5} \ \Rightarrow\ x = -6 \]
\[ 5\cdot(-6) + 9 = -30 + 9 = -21 \checkmark \]

Trying values of x in 5x + 9 = −21

x	5x + 9	Equals -21?
-8	-31	no
-7	-26	no
-6	-21	yes
-5	-16	no
-4	-11	no

Questions

What is x in 5x + 9 = −21?

The solution of 5x + 9 = −21 is x = -6.

How do you solve 5x + 9 = −21?

Subtract 9 from both sides to get 5x = -30, then divide both sides by 5 to get x = -6.

How do I check the answer?

Replace x by -6: 5(-6) + 9 = -21, which is -21.

Solve 5x + 9 = −21

How to work it out

Trying values of x in 5x + 9 = −21

Questions

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