We'll re-write the constraint x^2=2x-m moving all terms to
the left side.
x^2-2x+m =
0
Since we know that m represents the value of the product
of the roots, we'll write the Viete's 2nd relation:
x1*x2 =
m
From the module definition we'll write the given
constraint:
-1<(x1-x2)<1
If
we are square raising, we'll
get:
(x1-x2)^2=1
x1^2-2x1*x2+x2^2=1
x1^2+x2^2=1+2x1*x2
(1)
We know that if we are substituting the roots into the
equation, they are verifying it. So, we'll introduce the roots, one by one, into the
equation.
x1^2-2x1+m=0
(2)
x2^2-2x2+m=0 (3)
Now,
we'll add (2) and
(3):
x1^2-2x1+m+x2^2-2x2+m=0
We'll
combine like
terms:
(x1^2+x2^2)-2(x1+x2)+2m=0
From
the Viete's relations, we'll have:
x1+x2= -
(-2)/1
x1+x2= 2
So, x1^2+x2^2=
2(x1+x2)-2m, where x1+x2= 2
x1^2+x2^2= 2*2
-2m
x1^2+x2^2= 4-2m (4)
But
from relation (1), x1^2+x2^2=1+2x1*x2, where
x1*x2=m
From (1) and
(4):
We'll move the terms in m to the left side and the
numbers alone to the right
side:
4m=3
The
value of the product of the roots is m = 3/4.
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