21x^2-77=0

Solution for 21x^2-77=0 equation:

Simplifying
21x2 + -77 = 0

Reorder the terms:
-77 + 21x2 = 0

Solving
-77 + 21x2 = 0

Solving for variable 'x'.

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

Add '77' to each side of the equation.
-77 + 77 + 21x2 = 0 + 77

Combine like terms: -77 + 77 = 0
0 + 21x2 = 0 + 77
21x2 = 0 + 77

Combine like terms: 0 + 77 = 77
21x2 = 77

Divide each side by '21'.
x2 = 3.666666667

Simplifying
x2 = 3.666666667

Take the square root of each side:
x = {-1.914854216, 1.914854216}