Solve 6x + 15 = −21

The solution of 6x + 15 = −21 is x = -6.

6x + 15 = -21\ \Rightarrow\ x = -6

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The lines y = 6x + 15 and y = -21 meet at x = -6. 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.
$6x + 15 = -21$
2
Subtract 15 from both sides:
$6x + 15 - 15 = -21 - 15 \ \Rightarrow\ 6x = -36$
3
Divide both sides by 6:
$\frac{6x}{6} = \frac{-36}{6} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$6\cdot(-6) + 15 = -36 + 15 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 6x + 15 = -21\ \Rightarrow\ x = -6 \]
\[ 6x + 15 = -21 \]
\[ 6x + 15 - 15 = -21 - 15 \ \Rightarrow\ 6x = -36 \]
\[ \frac{6x}{6} = \frac{-36}{6} \ \Rightarrow\ x = -6 \]
\[ 6\cdot(-6) + 15 = -36 + 15 = -21 \checkmark \]

Trying values of x in 6x + 15 = −21

x	6x + 15	Equals -21?
-8	-33	no
-7	-27	no
-6	-21	yes
-5	-15	no
-4	-9	no

Questions

What is x in 6x + 15 = −21?

The solution of 6x + 15 = −21 is x = -6.

How do you solve 6x + 15 = −21?

Subtract 15 from both sides to get 6x = -36, then divide both sides by 6 to get x = -6.

How do I check the answer?

Replace x by -6: 6(-6) + 15 = -21, which is -21.

Solve 6x + 15 = −21

How to work it out

Trying values of x in 6x + 15 = −21

Questions

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