Solve 4x + 7 = −21

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

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

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

LaTeX source of the formulas on this page

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

Trying values of x in 4x + 7 = −21

x	4x + 7	Equals -21?
-9	-29	no
-8	-25	no
-7	-21	yes
-6	-17	no
-5	-13	no

Questions

What is x in 4x + 7 = −21?

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

How do you solve 4x + 7 = −21?

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

How do I check the answer?

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

Solve 4x + 7 = −21

How to work it out

Trying values of x in 4x + 7 = −21

Questions

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