We'll apply division with
reminder.
P=Q1*Q+R
The degree
of the the reminder has to be smaller than the degree of Q. In our case, Q has the
second degree, so the reminder is a first degree
polynomial.
R=aX+b
First,
let's find out the roots of
Q.
Q=(x+1)(x+2)
(x+1)(x+2) =
0
We'll put each factor as
zero.
(x+1) = 0
We'll add -1
both sides:
x = -1
x+2 =
0
We'll subtract 2 both
sides:
x = -2
Now, we'll
substitute the roots of Q, into the expression of division with
reminder.
P(-1) = Q(-1)*Q1+a*(-1)+b, where
P(-1)=1
But Q(-1)=0,
so:
1=0-a+b
-a+b=1
(1)
P(-2) = Q(-2)*Q2+a*(-2)+b, where
P(-2)=1
1=0-2a+b
-2a+b=1
(2)
From (1) and (2), we'll
have:
-a+b=-2a+b
We'll
eliminate like
terms:
-a=-2a
a=0, so 0+b=1,
b=1
R=a*X+b
R=0*X+1
R=1
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