Solve 5x + 4 = −21

The solution of 5x + 4 = −21 is x = -5.

5x + 4 = -21\ \Rightarrow\ x = -5

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The lines y = 5x + 4 and y = -21 meet at x = -5. 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.
$5x + 4 = -21$
2
Subtract 4 from both sides:
$5x + 4 - 4 = -21 - 4 \ \Rightarrow\ 5x = -25$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-25}{5} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$5\cdot(-5) + 4 = -25 + 4 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 5x + 4 = -21\ \Rightarrow\ x = -5 \]
\[ 5x + 4 = -21 \]
\[ 5x + 4 - 4 = -21 - 4 \ \Rightarrow\ 5x = -25 \]
\[ \frac{5x}{5} = \frac{-25}{5} \ \Rightarrow\ x = -5 \]
\[ 5\cdot(-5) + 4 = -25 + 4 = -21 \checkmark \]

Trying values of x in 5x + 4 = −21

x	5x + 4	Equals -21?
-7	-31	no
-6	-26	no
-5	-21	yes
-4	-16	no
-3	-11	no

Questions

What is x in 5x + 4 = −21?

The solution of 5x + 4 = −21 is x = -5.

How do you solve 5x + 4 = −21?

Subtract 4 from both sides to get 5x = -25, then divide both sides by 5 to get x = -5.

How do I check the answer?

Replace x by -5: 5(-5) + 4 = -21, which is -21.

Solve 5x + 4 = −21

How to work it out

Trying values of x in 5x + 4 = −21

Questions

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