How do you find all the zeros of f(x) = 3x^2 − 4x − 15?

2 Answers
Apr 7, 2018

Zeros of f(x) are x=3 and x= -5/3

Explanation:

f(x)=3x^2-4x-15 =3x^2-9x+5x-15

=3x(x-3)+5(x-3)= (x-3)(3x+5)

Zeros of f(x) are x=3 and x= -5/3 [Ans]

x=3,(-5)/3

Explanation:

Using trial and error method (x-3) is a factor of f(x)
I.e(x-3), x=3
f(3)=3(3^2)-4(3)-15
=3(9)-12-15
=27-12-15
=0
Using long division of polynomial's
(+)3x+5
root(x-3)(3x^2-4x-15)
((-)3x^2-9x)/(5x-15)
((-)5x-15)/(……)
Since x is in the 2nd degree, the 2 factors of f(x)are (x-3) and 3x+5
Equating factor to zero.
x-3=0,3x+5=0
x=3,3x=-5
x=3,x=(-5)/3(color (blue) (zero's. Of.f(x)))