Answer:
see below
Step-by-step explanation:
A. f(x) = 4x^2 - 7x - 15
We need the numbers to multiply to- 15
1*15 and 3*5
One of the terms multiplies by 4 (or 2)
Try 4 first
4*-3 +5 = -7 That works
-3+5 = -15
f(x) = (4x+5)(x-3)
B. We want the x intercepts so set equal to 0
0 = (4x+5)(x-3)
Using the zero product property
0 = 4x+5 x-3 =0
-5 = 4x x=3
-5/4 =x x=3
C End behavior
Let x be negative infinity
The function is dominate by 4x^2
f(-∞) = 4 ( -∞) ^2 = 4 (∞) = ∞
At negative infinity the functions goes to infinity
Let x be infinity
The function is dominate by 4x^2
f(∞) = 4 ( ∞) ^2 = 4 (∞) = ∞
At infinity the functions goes to infinity
Part D:
We know the zeros at 3 and -5/4
We know the vertex is at halfway between the zeros
(3 -5/4) /2 = 7/4 /2 = 7/8
Since the parabola opens up (The coefficient of the x^2 term is positive), we know we have a minimum.
f(7/8) = 4 (7/8)^2 -7(7/8) -15 = 4(49/64) -1/8 -15 =-289/16
We know the minimum the zeros and the end behavior, we can graph the functions