Determine how many, what type, and find the roots for f(x) = x4  + 21x2  − 100.

Step-by-step explanation:

We will make a substitution to make our work easier (when we get there).  We also need to know that

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

Therefore,

Now we will write the polynomial in terms of u instead of x:

Solve for the values of u by setting the polynomial equal to 0 and factoring.  When you factor, you will get:

But don't forget that

so we have to put those back in now:

By the Zero Product Property, either

or

We will factor the first term.  Solving for x-squared gives us:

and

x = ±√-25

which simplifies down to

x = ±√-1 × 25

we can sub in an i-squared for the -1:

x = ±√

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

, 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

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -