40r^2-42+9=0

Solution for 40r^2-42+9=0 equation:

Simplifying
40r2 + -42 + 9 = 0

Reorder the terms:
-42 + 9 + 40r2 = 0

Combine like terms: -42 + 9 = -33
-33 + 40r2 = 0

Solving
-33 + 40r2 = 0

Solving for variable 'r'.

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

Add '33' to each side of the equation.
-33 + 33 + 40r2 = 0 + 33

Combine like terms: -33 + 33 = 0
0 + 40r2 = 0 + 33
40r2 = 0 + 33

Combine like terms: 0 + 33 = 33
40r2 = 33

Divide each side by '40'.
r2 = 0.825

Simplifying
r2 = 0.825

Take the square root of each side:
r = {-0.908295106, 0.908295106}