I have a few problems I have having difficulty at arriving at a solution that fits correctly.

The first one solve the equation:

5x^2 - x - 1 = 0

The second seems to be very difficult for me:

The Function

f (x) = -0.02x^2 + x + 1

moldels the yearly growth of a young redwood tree, f (x), in inches, with x inches of rainfall per year. How many inches of rainfall per year result in maximum tree growth? What is the yearly growth?

The Third Problem:

Solve equation by making an appropriate substitution. When necessary check proposed solutions.

x^-2 + x^-1 - 56 = 0

Fourth Problem:

Express solution to equation in simplified form. Rationalize denominators. Solve equation by the square root property.

(x - 3)^2 = 20