Answer:
We need to find the zeros.
4x^4 + 8x^3 - 7x^2 -21x - 9
You're supposed to use synthetic division, assuming you're in algebra 2. I removed my calculus work.
x = -1 1/2, 1+sqrt5/2 , 1-sqrt5/2
x= -1.5000000119775176
4x 4 + 8x 3 - 7x 2 - 21x - 9= 0
x= -0.618033988749895
4x 4 + 8x 3 - 7x 2 - 21x - 9= 0
x= 1.618033988749895
4x 4 + 8x 3 - 7x 2 - 21x - 9= 0
