f(2)f(1)+1=4

Solution for f(2)f(1)+1=4 equation:

Simplifying
f(2) * f(1) + 1 = 4

Reorder the terms for easier multiplication:
2 * 1f * f + 1 = 4

Multiply 2 * 1
2f * f + 1 = 4

Multiply f * f
2f2 + 1 = 4

Reorder the terms:
1 + 2f2 = 4

Solving
1 + 2f2 = 4

Solving for variable 'f'.

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

Add '-1' to each side of the equation.
1 + -1 + 2f2 = 4 + -1

Combine like terms: 1 + -1 = 0
0 + 2f2 = 4 + -1
2f2 = 4 + -1

Combine like terms: 4 + -1 = 3
2f2 = 3

Divide each side by '2'.
f2 = 1.5

Simplifying
f2 = 1.5

Take the square root of each side:
f = {-1.224744871, 1.224744871}