SOLUTION: State two different ways to determine the number of zeros of the function f(x)=2(x+1)^2 -6

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Question 1193021: State two different ways to determine the number of zeros of the function
f(x)=2(x+1)^2 -6

Found 3 solutions by ikleyn, greenestamps, Edwin McCravy:
Answer by ikleyn(52887) About Me  (Show Source):
You can put this solution on YOUR website!
.

Use the Gauss theorem (another name: Fundamental Theorem of Algebra), which states that the number of (complex) roots

of any polynomial is equal to the degree of this polynomial.



See this Wikipedia article

https://en.wikipedia.org/wiki/Fundamental_theorem_of_algebra



Or derive your own formula for this simple quadratic equation, giving its roots explicitly (as Sir Edwin did in his post).




Answer by greenestamps(13209) About Me  (Show Source):
You can put this solution on YOUR website!


Technically, it is a polynomial of degree 2, so it has 2 zeros.

If you mean real zeros, then....

(1) Convert the equation to standard form ax%5E2%2Bbx%2Bc=0 and look at the discriminant b%5E2-4ac. There are 2 zeros if the discriminant is positive, 1 zero if it is 0, and no (real) zeros if it is negative.

(2) The equation as given is in vertex form. The vertex is (-1,-6) and the parabola opens upward, so there are 2 real zeros.


Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
Another way is to solve f(x) = 0 for x

2%28x%2B1%29%5E2-6=0

2%28x%2B1%29%5E2=6

%28x%2B1%29%5E2=3

x%2B1=%22%22+%2B-+sqrt%283%29

x=-1+%2B-+sqrt%283%29

One zero if you use the +, and another
if you use the -.  That makes 2 zeros.

Edwin