Use the graph to shorten the list of possible rational zeros of the function. Then find all real zeros of the function.

Question

1.) f(x)= 4x^3-8x^2-15x+9

4.) f(x)= 2x^3-5x^2-4x+10

Answer 1

who knows how to do this?

Answer 2

checking the graphs at wolframalpha.com,

http://www.wolframalpha.com/input/?i=4x^3-8x^2-15x%2B9

http://www.wolframalpha.com/input/?i=2x^3-5x^2-4x%2B10

it is clear that
#1 has a root at x = 3
#2 has a root at x = 5/2

So, divide through and you can use the quadratic formula to find the other roots.

Answer 3

the answer is wherever the graph hits the x axis.
1. -3/4, 1/2, 3
2. -3/2, 3/2, 5/2