Solve 2x − 7 = −21

The solution of 2x − 7 = −21 is x = -7.

2x - 7 = -21\ \Rightarrow\ x = -7

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The lines y = 2x − 7 and y = -21 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 subtraction, then the multiplication.
$2x - 7 = -21$
2
Add 7 to both sides:
$2x - 7 + 7 = -21 + 7 \ \Rightarrow\ 2x = -14$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{-14}{2} \ \Rightarrow\ x = -7$
4
Check: put x = -7 back into the equation.
$2\cdot(-7) - 7 = -14 - 7 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 7 = -21\ \Rightarrow\ x = -7 \]
\[ 2x - 7 = -21 \]
\[ 2x - 7 + 7 = -21 + 7 \ \Rightarrow\ 2x = -14 \]
\[ \frac{2x}{2} = \frac{-14}{2} \ \Rightarrow\ x = -7 \]
\[ 2\cdot(-7) - 7 = -14 - 7 = -21 \checkmark \]

Trying values of x in 2x − 7 = −21

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

Questions

What is x in 2x − 7 = −21?

The solution of 2x − 7 = −21 is x = -7.

How do you solve 2x − 7 = −21?

Add 7 to both sides to get 2x = -14, then divide both sides by 2 to get x = -7.

How do I check the answer?

Replace x by -7: 2(-7) − 7 = -21, which is -21.

Solve 2x − 7 = −21

How to work it out

Trying values of x in 2x − 7 = −21

Questions

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