Solve 3x − 9 = 0

The solution of 3x − 9 = 0 is x = 3.

3x - 9 = 0\ \Rightarrow\ x = 3

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

The lines y = 3x − 9 and y = 0 meet at x = 3. 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.
$3x - 9 = 0$
2
Add 9 to both sides:
$3x - 9 + 9 = 0 + 9 \ \Rightarrow\ 3x = 9$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{9}{3} \ \Rightarrow\ x = 3$
4
Check: put x = 3 back into the equation.
$3\cdot3 - 9 = 9 - 9 = 0 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 9 = 0\ \Rightarrow\ x = 3 \]
\[ 3x - 9 = 0 \]
\[ 3x - 9 + 9 = 0 + 9 \ \Rightarrow\ 3x = 9 \]
\[ \frac{3x}{3} = \frac{9}{3} \ \Rightarrow\ x = 3 \]
\[ 3\cdot3 - 9 = 9 - 9 = 0 \checkmark \]

Trying values of x in 3x − 9 = 0

x	3x − 9	Equals 0?
1	-6	no
2	-3	no
3	0	yes
4	3	no
5	6	no

Questions

What is x in 3x − 9 = 0?

The solution of 3x − 9 = 0 is x = 3.

How do you solve 3x − 9 = 0?

Add 9 to both sides to get 3x = 9, then divide both sides by 3 to get x = 3.

How do I check the answer?

Replace x by 3: 3(3) − 9 = 0, which is 0.

Solve 3x − 9 = 0

How to work it out

Trying values of x in 3x − 9 = 0

Questions

Similar equations