Find the equation that has 2, 1, and - 1 as roots

Answer: (x-2) (x-1) (x+1)

Step-by-step explanation: Roots are where the graph hits the x-axis. So just like if you had the equation (example) x^2 + 4x + 4 and you were to factor it out to get (x+2) (x+2) you could then set x+2=0 to get the root x=-2. Think of your problem like as if someone has already done the factoring for you. Now all you have to remember is that the answer will have the opposite sign with in the parentheses because its like you're adding or subtracting it to the x to get zero on other side of the equal sign ... x=3 - -> x-3 = 0