Question

Describe the error in solving the equation -2x^2+9x=4 using the Quadratic Formula.

Answer 1

The roots are 0.5 and 4.

Explanation:

-2x^2+9x=4

Rearrange:

-2x^2 + 9x - 4 = 0

x = [-b +/- √(b)^2 - 4ac)] / 2a

Using this quadratic formula the solution is:

x = [-9 +/- √(9)^2 - 4*(-2)*(-4)] / (2*-2)

= (-9 +/- √49) / -4

= 9/4 +/- (-7/4)

= 9/4 - 7/4 = 0.5

and 9/4 + 7/4 = 4