SOLUTION: please help me urgently.... 1)Find m and n if (x-2) and (x+3) are both factors of x^3+mx^2-nx-6 2) When p(x)=x^4-3x^3+ax^2+bx-6 is divided by (x+1)it has a remainder of 8. If (x

Algebra ->  Complex Numbers Imaginary Numbers Solvers and Lesson  -> Lesson -> SOLUTION: please help me urgently.... 1)Find m and n if (x-2) and (x+3) are both factors of x^3+mx^2-nx-6 2) When p(x)=x^4-3x^3+ax^2+bx-6 is divided by (x+1)it has a remainder of 8. If (x      Log On


   



Question 526662: please help me urgently....
1)Find m and n if (x-2) and (x+3) are both factors of x^3+mx^2-nx-6
2) When p(x)=x^4-3x^3+ax^2+bx-6 is divided by (x+1)it has a remainder of 8. If (x-3) is a factor of p(x) find a and b.
3) If x^2-4 is a factor of 2x^3-ax^2+bx+4 find a and b.

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
When you divide a polynomial P(x) by a divisor polynomial D(x) you get a quotient polynomial Q(x) and a remainder polynomial R(x). With some luck, all of those polynomial will be very small and simple, and maybe the remainder will be 0, or just a number (a polynomial of degree zero).
1) P%28x%29=x%5E3%2Bmx%5E2-nx-6=%28x-2%29Q%28x%29 (remainder is zero) means that
P%282%29=2%5E3%2Bm%282%5E2%29-2n-6=%282-2%29Q%282%29=0
8%2B4m-2n-6=0 or 4m-2n=-2
Similarly
P%28-3%29=0 leads you to 9m%2B3n=33
Those two equations form a linear system that allows you to find m and n.
2) Same idea
P%28x%29=%28x-3%29Q%28x%29 (remainder is zero) so P%283%29=0 and
P%28x%29=%28x%2B1%29Q%28x%29%2B8 (remainder is 8) so P%28-1%29=8
You'll get two equations that would allow you to find a and b.
3) P%28x%29=%28x%5E2-4%29Q%28x%29=%28x-2%29%28x%2B2%29Q%28x%29 (remainder is zero)
I would bet on
Q%28x%29=2x-1 and P%28x%29=%28x%5E2-4%29%282x-1%29
Multiplying will tell you if that product is a polynomial that could be the one you were given. (Easy way to solve it).
You are probably expected to use
P%282%29=0 and P%28-2%29=0
to set up a system of equations to solve for a and b, but who really enjoys solving systems of equations?