Question

Which is a zero of the quadratic function f(x) = 9x² – 54x - 19?

0 x = 1/3
0 x = 3 1/3
0x = 6 1/3
0 x = 9 1/3

Answer 1

6 1/3

Explanation:

when it is difficult to factorize, use abc formula

f((x) = 9x² – 54x - 19

a = 9

b = -54

c = -19

`x=(-b\±√(b^2-4ac) )/(2a)`

`x=(-(-54)\±√((-54)^2-4(9)(-19)) )/(2(9))`

`x=(54\±√(3600))/(18)`

`x=(54\±60 )/(18)`

x₁ = (54+60)/18

= 19/3

= 6 1/3

x₂ = (54-60)/18

= -1/3