Step by step
The question
Question: solve x² = 25.
x2 = 25
1 Square root of both sides
x squared is 25.
So x is the square root of 25, or minus it.
Minus times minus is plus, so the negative one works too.
x² = k → x = √k or x = −√k
5 × 5 = 25, (−5) × (−5) = 25
5 times 5 is 25.
So x = 5 or x = −5.
x = 5 or x = −5
Careful!
Many people write only x = 5.
They lose the minus answer.
Careful: not only x = 5 ✗
2 Check
Let's check: put x = 5 into the left side.
x = 5: 52 = 25
We get 25, the same as the right side.
It works!
Now put x = −5 into the left side.
x = −5: (−5)2 = 25
We get 25 again, the same as the right side.
So both answers are right!
Let's look back.
First: square root of both sides.
Last: check.
Answer
x = 5 or x = −5