Show that the given values for a and b are lower and upper bounds for the real zeros of the polynomial.?

Question

P(x)= x^4 -2x^3-9x^2+2x+8; a= -3, b=5

Answer 1

Use horner method to find zeros of polynomial

The real zeros of P(x)
are 1, -1,-2,4

sort these values

-2 , -1 , 1 , 4

Hence -3 is lower bound
and 5 is upper bound.