Answer:
Step-by-step explanation:
We will make a substitution to make our work easier (when we get there). We also need to know that
[tex]i^2=-1[/tex]
We will use that as another substitution. First, let's make the job of factoring a bit easier. Here's the first substitution. We will let
[tex]x^4=u^2[/tex]
Therefore,
[tex]x^2=u[/tex]
Now we will write the polynomial in terms of u instead of x:
[tex]f(x)=u^2+21u-100[/tex]
Solve for the values of u by setting the polynomial equal to 0 and factoring. When you factor, you will get:
[tex](u+25)(u-4)[/tex]
But don't forget that
[tex]x^2=u[/tex]
so we have to put those back in now:
[tex](x^2+25)(x^2-4)=0[/tex]
By the Zero Product Property, either
[tex]x^2+25=0[/tex] or
[tex]x^2-4=0[/tex]
We will factor the first term. Solving for x-squared gives us:
[tex]x^2=-25[/tex] and
x = ±√-25
which simplifies down to
x = ±√-1 × 25
we can sub in an i-squared for the -1:
x = ±√[tex]i^2*25[/tex]
The square root of i-squared is "i" and the square root of 25 is 5, so
x = ±5i
The next one is a bit easier. If
[tex]x^2=4[/tex], then
x = ±2
You can see you have 4 solutions. But you knew that already, since this is a 4th degree polynomial. The types of solutions are: 2 real, 2 imaginary
