Find the zeros of the polynomial function f(x) = 3x2 − 4x − 15.?

Question

A. 3, -4
B. -15, 3
C. 3, -5/3
D. -5/3, -4
E. -5, -3

Answer 1

f(x) = (3x+5)(x-3)
x = -5/3 and 3
Answer is C

Answer 2

If you have the answers to choose you find the zeros by testing... put each value in the x and avaluate.

If you do not have the answers, you may use the formula::

x = (-b +-sqrt(b^2 -4ac)/2a

Here a= 3 b=-4 c=-15

x = (4 +-sqrt(16+180)/6

x= (4 +-sqrt(l96))/6 = (4+-14)/6

then x = 18/6 = 3 or x = -10/6 = -5/3 option C

Answer 3

3x2 − 4x − 15

Discriminant = 16 +4(15)(3) = 16 +190 = 196 = 14^2

x1 = (4 - 14)/6 = -10/6 = -5/3
x2 = (4 +14)/6 =3

solution:

x1 = -5/3
x2 = 3

Answer 4

First you would factor the polynomial:

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

Then set each factor equal to zero and solve:

3x + 5 = 0 ..........and............x - 3 = 0
3x = -5...................................x = 3
x = -5/3

So, the answer is C.