Solve 9x − 3 = −21

The solution of 9x − 3 = −21 is x = -2.

9x - 3 = -21\ \Rightarrow\ x = -2

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The lines y = 9x − 3 and y = -21 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 subtraction, then the multiplication.
$9x - 3 = -21$
2
Add 3 to both sides:
$9x - 3 + 3 = -21 + 3 \ \Rightarrow\ 9x = -18$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-18}{9} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$9\cdot(-2) - 3 = -18 - 3 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 3 = -21\ \Rightarrow\ x = -2 \]
\[ 9x - 3 = -21 \]
\[ 9x - 3 + 3 = -21 + 3 \ \Rightarrow\ 9x = -18 \]
\[ \frac{9x}{9} = \frac{-18}{9} \ \Rightarrow\ x = -2 \]
\[ 9\cdot(-2) - 3 = -18 - 3 = -21 \checkmark \]

Trying values of x in 9x − 3 = −21

x	9x − 3	Equals -21?
-4	-39	no
-3	-30	no
-2	-21	yes
-1	-12	no
0	-3	no

Questions

What is x in 9x − 3 = −21?

The solution of 9x − 3 = −21 is x = -2.

How do you solve 9x − 3 = −21?

Add 3 to both sides to get 9x = -18, then divide both sides by 9 to get x = -2.

How do I check the answer?

Replace x by -2: 9(-2) − 3 = -21, which is -21.

Solve 9x − 3 = −21

How to work it out

Trying values of x in 9x − 3 = −21

Questions

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