Find the number of possible positive real zeros of f(x)=8x^4-72x^3+144x^2 a. four c. two or none b. three d. none select the best answer from the choices provided a b c d

  c.  two or none

Step-by-step explanation:

The signs of the coefficients are ...

  + - +

so there are two sign changes: + to -, and - to +. Descartes' rule of signs tells you to interpret this to mean there are 2 or 0 possible positive real roots.

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Pairs of roots are possibly complex, so the number of sign changes can be reduced by any even number to take that possibility into account. That is why 2 sign changes can mean either 2 or 0 positive real roots.

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A graph shows there to be 2 positive real roots and a root at x=0 with multiplicity 2. The latter should be no surprise, since x^2 is a factor of f(x).

5 - 25, 2.5, 0,5√2,5π

1/2 - 5/2, 1/4, 0, √2/2, √2/4, 1/2*π

0- 0, 0,0,0,0,0

√2- 5√2, √2/2, 0, ,2, 1, 4.448

1/√2- 5√2/2, √2/4, 0, 1, 2.22

π- 5π, 1/2*π, 0, 4.448, 1/2, 9.861