Solve 2x − 1 = 21

The solution of 2x − 1 = 21 is x = 11.

2x - 1 = 21\ \Rightarrow\ x = 11

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The lines y = 2x − 1 and y = 21 meet at x = 11. 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.
$2x - 1 = 21$
2
Add 1 to both sides:
$2x - 1 + 1 = 21 + 1 \ \Rightarrow\ 2x = 22$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{22}{2} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$2\cdot11 - 1 = 22 - 1 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 1 = 21\ \Rightarrow\ x = 11 \]
\[ 2x - 1 = 21 \]
\[ 2x - 1 + 1 = 21 + 1 \ \Rightarrow\ 2x = 22 \]
\[ \frac{2x}{2} = \frac{22}{2} \ \Rightarrow\ x = 11 \]
\[ 2\cdot11 - 1 = 22 - 1 = 21 \checkmark \]

Trying values of x in 2x − 1 = 21

x	2x − 1	Equals 21?
9	17	no
10	19	no
11	21	yes
12	23	no
13	25	no

Questions

What is x in 2x − 1 = 21?

The solution of 2x − 1 = 21 is x = 11.

How do you solve 2x − 1 = 21?

Add 1 to both sides to get 2x = 22, then divide both sides by 2 to get x = 11.

How do I check the answer?

Replace x by 11: 2(11) − 1 = 21, which is 21.

Solve 2x − 1 = 21

How to work it out

Trying values of x in 2x − 1 = 21

Questions

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