3x^2-21=126

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Solution for 3x^2-21=126 equation:


Simplifying
3x2 + -21 = 126

Reorder the terms:
-21 + 3x2 = 126

Solving
-21 + 3x2 = 126

Solving for variable 'x'.

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

Add '21' to each side of the equation.
-21 + 21 + 3x2 = 126 + 21

Combine like terms: -21 + 21 = 0
0 + 3x2 = 126 + 21
3x2 = 126 + 21

Combine like terms: 126 + 21 = 147
3x2 = 147

Divide each side by '3'.
x2 = 49

Simplifying
x2 = 49

Take the square root of each side:
x = {-7, 7}

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