18+x(1-4x)=42

Solution for 18+x(1-4x)=42 equation:

Simplifying
18 + x(1 + -4x) = 42
18 + (1 * x + -4x * x) = 42
18 + (1x + -4x2) = 42

Solving
18 + 1x + -4x2 = 42

Solving for variable 'x'.

Reorder the terms:
18 + -42 + 1x + -4x2 = 42 + -42

Combine like terms: 18 + -42 = -24
-24 + 1x + -4x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-24 + 1x + -4x2 = 0

Begin completing the square.  Divide all terms by
-4 the coefficient of the squared term: 

Divide each side by '-4'.
6 + -0.25x + x2 = 0

Move the constant term to the right:

Add '-6' to each side of the equation.
6 + -0.25x + -6 + x2 = 0 + -6

Reorder the terms:
6 + -6 + -0.25x + x2 = 0 + -6

Combine like terms: 6 + -6 = 0
0 + -0.25x + x2 = 0 + -6
-0.25x + x2 = 0 + -6

Combine like terms: 0 + -6 = -6
-0.25x + x2 = -6

The x term is -0.25x.  Take half its coefficient (-0.125).
Square it (0.015625) and add it to both sides.

Add '0.015625' to each side of the equation.
-0.25x + 0.015625 + x2 = -6 + 0.015625

Reorder the terms:
0.015625 + -0.25x + x2 = -6 + 0.015625

Combine like terms: -6 + 0.015625 = -5.984375
0.015625 + -0.25x + x2 = -5.984375

Factor a perfect square on the left side:
(x + -0.125)(x + -0.125) = -5.984375

Can't calculate square root of the right side.

The solution to this equation could not be determined.