90=(2-w)(5+w)

Solution for 90=(2-w)(5+w) equation:

Simplifying
90 = (2 + -1w)(5 + w)

Multiply (2 + -1w) * (5 + w)
90 = (2(5 + w) + -1w * (5 + w))
90 = ((5 * 2 + w * 2) + -1w * (5 + w))
90 = ((10 + 2w) + -1w * (5 + w))
90 = (10 + 2w + (5 * -1w + w * -1w))
90 = (10 + 2w + (-5w + -1w2))

Combine like terms: 2w + -5w = -3w
90 = (10 + -3w + -1w2)

Solving
90 = 10 + -3w + -1w2

Solving for variable 'w'.

Combine like terms: 90 + -10 = 80
80 + 3w + w2 = 10 + -3w + -1w2 + -10 + 3w + w2

Reorder the terms:
80 + 3w + w2 = 10 + -10 + -3w + 3w + -1w2 + w2

Combine like terms: 10 + -10 = 0
80 + 3w + w2 = 0 + -3w + 3w + -1w2 + w2
80 + 3w + w2 = -3w + 3w + -1w2 + w2

Combine like terms: -3w + 3w = 0
80 + 3w + w2 = 0 + -1w2 + w2
80 + 3w + w2 = -1w2 + w2

Combine like terms: -1w2 + w2 = 0
80 + 3w + w2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-80' to each side of the equation.
80 + 3w + -80 + w2 = 0 + -80

Reorder the terms:
80 + -80 + 3w + w2 = 0 + -80

Combine like terms: 80 + -80 = 0
0 + 3w + w2 = 0 + -80
3w + w2 = 0 + -80

Combine like terms: 0 + -80 = -80
3w + w2 = -80

The w term is 3w.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3w + 2.25 + w2 = -80 + 2.25

Reorder the terms:
2.25 + 3w + w2 = -80 + 2.25

Combine like terms: -80 + 2.25 = -77.75
2.25 + 3w + w2 = -77.75

Factor a perfect square on the left side:
(w + 1.5)(w + 1.5) = -77.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.