0=a^2-8a+42

Solution for 0=a^2-8a+42 equation:

Simplifying
0 = a2 + -8a + 42

Reorder the terms:
0 = 42 + -8a + a2

Solving
0 = 42 + -8a + a2

Solving for variable 'a'.

Combine like terms: 0 + -42 = -42
-42 + 8a + -1a2 = 42 + -8a + a2 + -42 + 8a + -1a2

Reorder the terms:
-42 + 8a + -1a2 = 42 + -42 + -8a + 8a + a2 + -1a2

Combine like terms: 42 + -42 = 0
-42 + 8a + -1a2 = 0 + -8a + 8a + a2 + -1a2
-42 + 8a + -1a2 = -8a + 8a + a2 + -1a2

Combine like terms: -8a + 8a = 0
-42 + 8a + -1a2 = 0 + a2 + -1a2
-42 + 8a + -1a2 = a2 + -1a2

Combine like terms: a2 + -1a2 = 0
-42 + 8a + -1a2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
42 + -8a + a2 = 0

Move the constant term to the right:

Add '-42' to each side of the equation.
42 + -8a + -42 + a2 = 0 + -42

Reorder the terms:
42 + -42 + -8a + a2 = 0 + -42

Combine like terms: 42 + -42 = 0
0 + -8a + a2 = 0 + -42
-8a + a2 = 0 + -42

Combine like terms: 0 + -42 = -42
-8a + a2 = -42

The a term is -8a.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8a + 16 + a2 = -42 + 16

Reorder the terms:
16 + -8a + a2 = -42 + 16

Combine like terms: -42 + 16 = -26
16 + -8a + a2 = -26

Factor a perfect square on the left side:
(a + -4)(a + -4) = -26

Can't calculate square root of the right side.

The solution to this equation could not be determined.