Question

2x cubed -4x sq.+ 8x -3 x=-2

Answer 1

f(x) = 2x^3 - 4x^2 + 8x - 3

so, if x = -2, just replace all the x's with (-2)'s:

f(-2) = 2(-2)^3 - 4(-2)^2 + 8(-2) - 3
= 2(-8) - 4(4) + 8(-2) - 3
= -16 - 16 - 16 - 3
= -51

Note how much clearer using ^ for powers is than all that wordy mumbo-jumbo.

Answer 2

2 x^3 - 4 x^2 + 5 x + 2 = 0 ??????
I suspect a typo and you do not say what you want. I assume roots.
using
http://www.mathportal.org/calculators/polynomials-solvers/polynomial-roots-calculator.php

x1=−0.31075

x2=1.15537+1.37229∗i

x3=1.15537−1.37229∗i

Answer 3

I did not understand your question.

Answer 4

since no question was posed, just a murky and cryptic expression.

Next time, SHAELYNNN, try to be it clear just what it is you need help with. We tend to ignore postings where we have to figure out the question as well as the answer!