Quadratic equations – solving quadratic equations by use of quadratic formula

Solve the quadratic equation 2r² - r – 3 = 0

Solution

Step1

Given that 2r² - r – 3 = 0

We have to first compare this equation with the general form of quadratic equation ax² + bx + c = 0

The reason is to enable us determine the values of a, b and c respectively, which are required for substitution in the formula.

Step2

Compare the equations

ax² + bx + c = 0

2r² - r – 3 = 0

By comparison, we notice that a=2, b=-1 and c=-3 (taking x in the formula to be r in the question)

Step3

Substitute as follows