Solve 7x + 7 = −21

The solution of 7x + 7 = −21 is x = -4.

7x + 7 = -21\ \Rightarrow\ x = -4

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The lines y = 7x + 7 and y = -21 meet at x = -4. 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.
$7x + 7 = -21$
2
Subtract 7 from both sides:
$7x + 7 - 7 = -21 - 7 \ \Rightarrow\ 7x = -28$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-28}{7} \ \Rightarrow\ x = -4$
4
Check: put x = -4 back into the equation.
$7\cdot(-4) + 7 = -28 + 7 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 7x + 7 = -21\ \Rightarrow\ x = -4 \]
\[ 7x + 7 = -21 \]
\[ 7x + 7 - 7 = -21 - 7 \ \Rightarrow\ 7x = -28 \]
\[ \frac{7x}{7} = \frac{-28}{7} \ \Rightarrow\ x = -4 \]
\[ 7\cdot(-4) + 7 = -28 + 7 = -21 \checkmark \]

Trying values of x in 7x + 7 = −21

x	7x + 7	Equals -21?
-6	-35	no
-5	-28	no
-4	-21	yes
-3	-14	no
-2	-7	no

Questions

What is x in 7x + 7 = −21?

The solution of 7x + 7 = −21 is x = -4.

How do you solve 7x + 7 = −21?

Subtract 7 from both sides to get 7x = -28, then divide both sides by 7 to get x = -4.

How do I check the answer?

Replace x by -4: 7(-4) + 7 = -21, which is -21.

Solve 7x + 7 = −21

How to work it out

Trying values of x in 7x + 7 = −21

Questions

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