Solve 2x − 9 = −21

The solution of 2x − 9 = −21 is x = -6.

2x - 9 = -21\ \Rightarrow\ x = -6

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The lines y = 2x − 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 subtraction, then the multiplication.
$2x - 9 = -21$
2
Add 9 to both sides:
$2x - 9 + 9 = -21 + 9 \ \Rightarrow\ 2x = -12$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{-12}{2} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$2\cdot(-6) - 9 = -12 - 9 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 9 = -21\ \Rightarrow\ x = -6 \]
\[ 2x - 9 = -21 \]
\[ 2x - 9 + 9 = -21 + 9 \ \Rightarrow\ 2x = -12 \]
\[ \frac{2x}{2} = \frac{-12}{2} \ \Rightarrow\ x = -6 \]
\[ 2\cdot(-6) - 9 = -12 - 9 = -21 \checkmark \]

Trying values of x in 2x − 9 = −21

x	2x − 9	Equals -21?
-8	-25	no
-7	-23	no
-6	-21	yes
-5	-19	no
-4	-17	no

Questions

What is x in 2x − 9 = −21?

The solution of 2x − 9 = −21 is x = -6.

How do you solve 2x − 9 = −21?

Add 9 to both sides to get 2x = -12, then divide both sides by 2 to get x = -6.

How do I check the answer?

Replace x by -6: 2(-6) − 9 = -21, which is -21.

Solve 2x − 9 = −21

How to work it out

Trying values of x in 2x − 9 = −21

Questions

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