40=(u+3)(u-3)

Solution for 40=(u+3)(u-3) equation:

Simplifying
40 = (u + 3)(u + -3)

Reorder the terms:
40 = (3 + u)(u + -3)

Reorder the terms:
40 = (3 + u)(-3 + u)

Multiply (3 + u) * (-3 + u)
40 = (3(-3 + u) + u(-3 + u))
40 = ((-3 * 3 + u * 3) + u(-3 + u))
40 = ((-9 + 3u) + u(-3 + u))
40 = (-9 + 3u + (-3 * u + u * u))
40 = (-9 + 3u + (-3u + u2))

Combine like terms: 3u + -3u = 0
40 = (-9 + 0 + u2)
40 = (-9 + u2)

Solving
40 = -9 + u2

Solving for variable 'u'.

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

Add '-1u2' to each side of the equation.
40 + -1u2 = -9 + u2 + -1u2

Combine like terms: u2 + -1u2 = 0
40 + -1u2 = -9 + 0
40 + -1u2 = -9

Add '-40' to each side of the equation.
40 + -40 + -1u2 = -9 + -40

Combine like terms: 40 + -40 = 0
0 + -1u2 = -9 + -40
-1u2 = -9 + -40

Combine like terms: -9 + -40 = -49
-1u2 = -49

Divide each side by '-1'.
u2 = 49

Simplifying
u2 = 49

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