Find the value of the product of roots of this

tripplek7i

tripplek7i

Answered question

2022-01-30

Find the value of the product of roots of this quadratic equation
It is given that one of the roots of the quadratic equation :
x2+(p+3)xp2=0

Answer & Explanation

coolbananas03ok

coolbananas03ok

Beginner2022-01-31Added 20 answers

Step 1
Without applying the factorization of a "difference of two squares" or Viete's relations, we can still use the information stated in the problem. If we call the two roots of the quadratic equation r and -r , then we have
r2+(p+3)×rp2=0
and
[r]2+(p+3)×[r]p2
=r2(p+3)×rp2=0
This means that
r2=(p+3)×r+p2
=(p+3)×r+p22×(p+3)×r=0
So either r=0 or p=3
But if r=0=r, then
02+(p+3)×0p2=0 would reqiure p=0,
which would then make the quadratic equation
x3+3×x=0
But that polynomial factors as
x×(x+3)=0,
so we couldn't have both roots equal to zero.
Instead, it must be that p=3, making the equation
x2+0×x(3)2=x29=0,
for which the roots are given by
r2=9r=+3, 3;
the product of the roots is thus -9
Step 2
Another way to arrive at this conclusion is that
y=x2+(p+3)×xp2
is the equation of an "upward-opening" parabola, for which we want the x-intercepts to be x=r and x=r. Its axis of symmetry is located midway between these intercepts, so we have h=0 in the "vertex form" of the parabola's equation,
y=(x0)2p2
(The vertex is definitely "below" the x-axis at (0, p2), so we know these x-intercepts exist.) The equation of the parabola is therefore y=x2p2, making p+3=0 and the rest of the argument above follows.

lirwerwammete9t

lirwerwammete9t

Beginner2022-02-01Added 9 answers

Step 1
We know that this equation has at most two roots in the set of reals.
Let's denote them with a and -a.
Then your equation is
x2a2=0.
Therefore p must be equal to -3.
Hence the equation is
x29=0
and the roots are 3 and -3. So the desired product is -9.

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