Question

draw the graph of the polynomial and find the zeroes also justify your answer.if f(x)=x2-2x-15​

Answer 1

f(x)=x2−2x−8

to find the vertex, we know,

x=−2ab=−2×1−2=1

to find y coordinate, substitute the value of x in equation.

(1)2−2(1)−8=1−2−8=9

The vertex is (1,9)

Now, x intercepts,

x2−2x−8=0

(x−4)(x+2)=0

x=−2,4

The x intercepts are (−2,0),(4,0)

To find the y intercept, substitute x=0 in given equation,

02−2(0)−8=−8

The y intercept is (0,−8)

Thus it is an upward facing parabola, touching x and y axis at (2,−8),(−1,−5),(3,−5)