Solve 8x + 1 = 81

The solution of 8x + 1 = 81 is x = 10.

8x + 1 = 81\ \Rightarrow\ x = 10

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The lines y = 8x + 1 and y = 81 meet at x = 10. 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.
$8x + 1 = 81$
2
Subtract 1 from both sides:
$8x + 1 - 1 = 81 - 1 \ \Rightarrow\ 8x = 80$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{80}{8} \ \Rightarrow\ x = 10$
4
Check: put x = 10 back into the equation.
$8\cdot10 + 1 = 80 + 1 = 81 \checkmark$

LaTeX source of the formulas on this page

\[ 8x + 1 = 81\ \Rightarrow\ x = 10 \]
\[ 8x + 1 = 81 \]
\[ 8x + 1 - 1 = 81 - 1 \ \Rightarrow\ 8x = 80 \]
\[ \frac{8x}{8} = \frac{80}{8} \ \Rightarrow\ x = 10 \]
\[ 8\cdot10 + 1 = 80 + 1 = 81 \checkmark \]

Trying values of x in 8x + 1 = 81

x	8x + 1	Equals 81?
8	65	no
9	73	no
10	81	yes
11	89	no
12	97	no

Questions

What is x in 8x + 1 = 81?

The solution of 8x + 1 = 81 is x = 10.

How do you solve 8x + 1 = 81?

Subtract 1 from both sides to get 8x = 80, then divide both sides by 8 to get x = 10.

How do I check the answer?

Replace x by 10: 8(10) + 1 = 81, which is 81.

Solve 8x + 1 = 81

How to work it out

Trying values of x in 8x + 1 = 81

Questions

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