Question

Please help/explain...?

Answer 1

http://www.mathwords.com/r/rational_root_theorem.htm check this out

Answer 2

Just substitute all the values that are given into the equation. If the final answer is equal to 0, then it is the right one.

Example,
Your equation is 12x^3 + 14x^2 - x + 18 = 0
Then just subtitute 1/9 or -1/9 into the equation.
12(1/9)^3 + 14(1/9)^2 - (1/9) + 18
And your answer must be equal to 0.

Answer 3

*I mean substitute 1/4/ or -1/4
And 2/3 or -2/3