21x^2-(21*9+-9)=0

Solution for 21x^2-(21*9+-9)=0 equation:

Simplifying
21x2 + -1(21 * 9 + -9) = 0

Multiply 21 * 9
21x2 + -1(189 + -9) = 0

Combine like terms: 189 + -9 = 180
21x2 + -1(180) = 0

Multiply -1 * 180
21x2 + -180 = 0

Reorder the terms:
-180 + 21x2 = 0

Solving
-180 + 21x2 = 0

Solving for variable 'x'.

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

Add '180' to each side of the equation.
-180 + 180 + 21x2 = 0 + 180

Combine like terms: -180 + 180 = 0
0 + 21x2 = 0 + 180
21x2 = 0 + 180

Combine like terms: 0 + 180 = 180
21x2 = 180

Divide each side by '21'.
x2 = 8.571428571

Simplifying
x2 = 8.571428571

Take the square root of each side:
x = {-2.927700219, 2.927700219}