Use the quadratic formula to find the roots of the equation. Round to tenths if necessary.x^2+3x-18

Question

Use the quadratic formula to find the roots of the equation.  Round to tenths if necessary.  Write your solution in set brackets with no spaces, such as {-1,2}.

Answer 1

The quadratic factorises: (x+6)(x-3). Setting the quadratic to zero gives roots x=-6 or 3 or { -6 3 }.

Using the formula, x=(-3+sqrt(9+72))/2=(-3+9)/2=6/2=3 or -12/2=-6, which is the same result.