2x(x-4)=42

Solution for 2x(x-4)=42 equation:

Simplifying
2x(x + -4) = 42

Reorder the terms:
2x(-4 + x) = 42
(-4 * 2x + x * 2x) = 42
(-8x + 2x2) = 42

Solving
-8x + 2x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + -8x + 2x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + -8x + 2x2 = 0

Factor out the Greatest Common Factor (GCF), '2'.
2(-21 + -4x + x2) = 0

Factor a trinomial.
2((-3 + -1x)(7 + -1x)) = 0

Ignore the factor 2.
Subproblem 1
Set the factor '(-3 + -1x)' equal to zero and attempt to solve:

Simplifying
-3 + -1x = 0

Solving
-3 + -1x = 0

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

Add '3' to each side of the equation.
-3 + 3 + -1x = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -1x = 0 + 3
-1x = 0 + 3

Combine like terms: 0 + 3 = 3
-1x = 3

Divide each side by '-1'.
x = -3

Simplifying
x = -3
Subproblem 2
Set the factor '(7 + -1x)' equal to zero and attempt to solve:

Simplifying
7 + -1x = 0

Solving
7 + -1x = 0

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

Add '-7' to each side of the equation.
7 + -7 + -1x = 0 + -7

Combine like terms: 7 + -7 = 0
0 + -1x = 0 + -7
-1x = 0 + -7

Combine like terms: 0 + -7 = -7
-1x = -7

Divide each side by '-1'.
x = 7

Simplifying
x = 7
Solution
x = {-3, 7}