x^2-4=21

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Solution for x^2-4=21 equation: 


Simplifying
x2 + -4 = 21

Reorder the terms:
-4 + x2 = 21

Solving
-4 + x2 = 21

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '4' to each side of the equation.
-4 + 4 + x2 = 21 + 4

Combine like terms: -4 + 4 = 0
0 + x2 = 21 + 4
x2 = 21 + 4

Combine like terms: 21 + 4 = 25
x2 = 25

Simplifying
x2 = 25

Take the square root of each side:
x = {-5, 5}

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