(y+.3)(y-3.5)=0

Solution for (y+.3)(y-3.5)=0 equation:

Simplifying
(y + 0.3)(y + -3.5) = 0

Reorder the terms:
(0.3 + y)(y + -3.5) = 0

Reorder the terms:
(0.3 + y)(-3.5 + y) = 0

Multiply (0.3 + y) * (-3.5 + y)
(0.3(-3.5 + y) + y(-3.5 + y)) = 0
((-3.5 * 0.3 + y * 0.3) + y(-3.5 + y)) = 0
((-1.05 + 0.3y) + y(-3.5 + y)) = 0
(-1.05 + 0.3y + (-3.5 * y + y * y)) = 0
(-1.05 + 0.3y + (-3.5y + y2)) = 0

Combine like terms: 0.3y + -3.5y = -3.2y
(-1.05 + -3.2y + y2) = 0

Solving
-1.05 + -3.2y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '1.05' to each side of the equation.
-1.05 + -3.2y + 1.05 + y2 = 0 + 1.05

Reorder the terms:
-1.05 + 1.05 + -3.2y + y2 = 0 + 1.05

Combine like terms: -1.05 + 1.05 = 0.00
0.00 + -3.2y + y2 = 0 + 1.05
-3.2y + y2 = 0 + 1.05

Combine like terms: 0 + 1.05 = 1.05
-3.2y + y2 = 1.05

The y term is -3.2y.  Take half its coefficient (-1.6).
Square it (2.56) and add it to both sides.

Add '2.56' to each side of the equation.
-3.2y + 2.56 + y2 = 1.05 + 2.56

Reorder the terms:
2.56 + -3.2y + y2 = 1.05 + 2.56

Combine like terms: 1.05 + 2.56 = 3.61
2.56 + -3.2y + y2 = 3.61

Factor a perfect square on the left side:
(y + -1.6)(y + -1.6) = 3.61

Calculate the square root of the right side: 1.9

Break this problem into two subproblems by setting 
(y + -1.6) equal to 1.9 and -1.9.

Subproblem 1
y + -1.6 = 1.9

Simplifying
y + -1.6 = 1.9

Reorder the terms:
-1.6 + y = 1.9

Solving
-1.6 + y = 1.9

Solving for variable 'y'.

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

Add '1.6' to each side of the equation.
-1.6 + 1.6 + y = 1.9 + 1.6

Combine like terms: -1.6 + 1.6 = 0.0
0.0 + y = 1.9 + 1.6
y = 1.9 + 1.6

Combine like terms: 1.9 + 1.6 = 3.5
y = 3.5

Simplifying
y = 3.5

Subproblem 2
y + -1.6 = -1.9

Simplifying
y + -1.6 = -1.9

Reorder the terms:
-1.6 + y = -1.9

Solving
-1.6 + y = -1.9

Solving for variable 'y'.

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

Add '1.6' to each side of the equation.
-1.6 + 1.6 + y = -1.9 + 1.6

Combine like terms: -1.6 + 1.6 = 0.0
0.0 + y = -1.9 + 1.6
y = -1.9 + 1.6

Combine like terms: -1.9 + 1.6 = -0.3
y = -0.3

Simplifying
y = -0.3

Solution
The solution to the problem is based on the solutions
from the subproblems.
y = {3.5, -0.3}