Question

Is the answer E ?

http://img17.imageshack.us/img17/8670/andysnap009.png

Answer 1

If your answer's E, when you sub. x=b in, you don't get zero. You should get zero because it's a root of the polynomial.

Answer 2

but isn't (x+2)^2 .. -2 to the left..?

Answer 3

b is in the positive side of the number line.

Answer 4

Two other things to consider - the shape of the graph is such that the coefficient of x^3 is negative, and there's a double root at a since it just touches the axis and there are no complex roots (if there were, it would look different).

Answer 5

Those three pieces of information should kill four of the five possibilities.

Answer 6

but b is (x-b)^2

Answer 7

shouldnt that be to the right

Answer 8

sorry (x-a)^2

Answer 9

or do we count the negative outside the bracket as well?

Answer 10

The negative outside the bracket is allowing you to have a negative coefficient on x^3, which is what you need.

Answer 11

Do you want me to go through them?

Answer 12

yes please

Answer 13

Well, A is out because the coefficient of x^3 will be positive.

Answer 14

C, D, E are out because you have a double root at a, which means the factor containing a should be raised to the power of 2.

Answer 15

Leaves B

Answer 16

ohhh I get it now :) Thanks for your time :)

Answer 17

No probs.