Solve 7x − 7 = −21

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

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

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

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

LaTeX source of the formulas on this page

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

Trying values of x in 7x − 7 = −21

x	7x − 7	Equals -21?
-4	-35	no
-3	-28	no
-2	-21	yes
-1	-14	no
0	-7	no

Questions

What is x in 7x − 7 = −21?

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

How do you solve 7x − 7 = −21?

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

How do I check the answer?

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

Solve 7x − 7 = −21

How to work it out

Trying values of x in 7x − 7 = −21

Questions

Similar equations