Question

1. Find the actual zero of f(x) = x3 + 5x2 - 4x - 20?

i really need help on this :(

Answer 1

Any idea? Hint: have to use "try and error" method. plug \(\pm1, \pm2\) to get the first zero, then use long division or synthetic to get the leftover.

Answer 2

i have no idea what any of that is.

Answer 3

Show me your trying, please, plug x = 1, x =-1, x =2, x=-2 into the original one, what do you get for f(x)?

Answer 4

You can rearrange the terms and do some factoring:
x^3 + 5x^2 - 4x - 20
=x^3-4x+5x^2-20
=x(x^2-4)+5x^2-20
=x(x^2-4)+5(x^2-4)
=(x+5)(x^2-4)
=(x+5)(x+2)(x-2)
So zeroes are: -5,-2,+2