Question

Use the function f(x) = 4x² - 7x - 15 to answer the questions.

Part A: Completely factor f(x). (2 points)

Part B: What are the x-intercepts of the graph of f(x)? Show your work. (2 points)

Part C: Describe the end behavior of the graph of f(x). Explain. (2 points)

Part D: What are the steps you would use to graph f(x)? Justify that you can use the answers obtained in Part B and Part C to draw the graph.​

Answer 1

Explanation:

Part A:

4x² - 7x - 15

a, b, c = 4, -7, -15

ac = -60

factors that add up to -7 and multiply to -60 are (-12, 5)

rewrite equation

(4x² - 12x) + (5x - 15)

factor out GCF from both groups

4x(x - 3) + 5(x - 3)

(4x+5)(x-3)

Part B:

Using the factored form from the previous part we can set both factors equal to 0 to solve for x.

4x+5 = 0

4x = -5

x = -5/4

x-3 = 0

x = 3

the two x-intercepts are -5/4 and 3

Part C:

Since the leading coefficient is positive, the right side of the function will be going up or to positive infinity as x goes towards positive infinity. Since the degree is even both sides go in the same direction so on the left side it also goes towards positive infinity as x goes towards negative infinity.