4x^2-9=21

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Solution for 4x^2-9=21 equation:


Simplifying
4x2 + -9 = 21

Reorder the terms:
-9 + 4x2 = 21

Solving
-9 + 4x2 = 21

Solving for variable 'x'.

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

Add '9' to each side of the equation.
-9 + 9 + 4x2 = 21 + 9

Combine like terms: -9 + 9 = 0
0 + 4x2 = 21 + 9
4x2 = 21 + 9

Combine like terms: 21 + 9 = 30
4x2 = 30

Divide each side by '4'.
x2 = 7.5

Simplifying
x2 = 7.5

Take the square root of each side:
x = {-2.738612788, 2.738612788}

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