Question

Use the quadratic formula to solve this equation to 3sf: 5x^2-2x-11=0

Answer 1

X=1/5+2/5√14 or 1/5 + -2/5√14

Answer 2

The quadratic formula is the result of completing the square for ax^2+bx+c=0 and it is:

x=(-b±√(b^2-4ac))/(2a)  in this case:

x=(2±√(4-4(5)(-11))/(2(5))

x=(2±√224)/10

x=(2±4√14)/10

x=(1±2√14)/5

x≈(-1.30, 1.70)  (to three significant figures)