Solve 6x − 9 = −21

The solution of 6x − 9 = −21 is x = -2.

6x - 9 = -21\ \Rightarrow\ x = -2

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

The lines y = 6x − 9 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.
$6x - 9 = -21$
2
Add 9 to both sides:
$6x - 9 + 9 = -21 + 9 \ \Rightarrow\ 6x = -12$
3
Divide both sides by 6:
$\frac{6x}{6} = \frac{-12}{6} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$6\cdot(-2) - 9 = -12 - 9 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 6x - 9 = -21\ \Rightarrow\ x = -2 \]
\[ 6x - 9 = -21 \]
\[ 6x - 9 + 9 = -21 + 9 \ \Rightarrow\ 6x = -12 \]
\[ \frac{6x}{6} = \frac{-12}{6} \ \Rightarrow\ x = -2 \]
\[ 6\cdot(-2) - 9 = -12 - 9 = -21 \checkmark \]

Trying values of x in 6x − 9 = −21

x	6x − 9	Equals -21?
-4	-33	no
-3	-27	no
-2	-21	yes
-1	-15	no
0	-9	no

Questions

What is x in 6x − 9 = −21?

The solution of 6x − 9 = −21 is x = -2.

How do you solve 6x − 9 = −21?

Add 9 to both sides to get 6x = -12, then divide both sides by 6 to get x = -2.

How do I check the answer?

Replace x by -2: 6(-2) − 9 = -21, which is -21.

Solve 6x − 9 = −21

How to work it out

Trying values of x in 6x − 9 = −21

Questions

Similar equations