3.1x^2-4.2-7.8=0

Solution for 3.1x^2-4.2-7.8=0 equation:

Simplifying
3.1x2 + -4.2 + -7.8 = 0

Reorder the terms:
-4.2 + -7.8 + 3.1x2 = 0

Combine like terms: -4.2 + -7.8 = -12
-12 + 3.1x2 = 0

Solving
-12 + 3.1x2 = 0

Solving for variable 'x'.

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

Add '12' to each side of the equation.
-12 + 12 + 3.1x2 = 0 + 12

Combine like terms: -12 + 12 = 0
0 + 3.1x2 = 0 + 12
3.1x2 = 0 + 12

Combine like terms: 0 + 12 = 12
3.1x2 = 12

Divide each side by '3.1'.
x2 = 3.870967742

Simplifying
x2 = 3.870967742

Take the square root of each side:
x = {-1.967477507, 1.967477507}