Q1 of 64 Page 49

State whether the following statements are true or false:

(1) is a zero of the linear polynomial p(x) = 5x + 7.


(2) p(x) = x2 + 2x + 1 has two distinct zeros.


(3) The cubic polynomial p(x) = x3 + x2 — x — 1 has two distinct zeros.


(4) The graph of the cubic polynomial p(x) = x3 meets the X—axis at only one point.


(5) Any quadratic polynomial p(x) has at least one zero, x R

(1) p(x) = 5x + 7


p = 5 + 7 = 14


p ≠0


is not a zero of p(x).


So the statement is False.


(2) Given, p(x) = x2 + 2x + 1


To find the zeros of p(x), let p(x) = 0


x2 + 2x + 1 = 0


(x + 1)2 = 0 Using the identity: (a+ b) 2 = (a2 + 2ab + b2)


x + 1 = 0 or x = –1


x = –1 or x = –1


Here, both the zeros are equal, i.e. –1, and hence not distinct.


So the statement is False.


(3) Given, p(x) = x3 + x2 — x — 1


To find the zeros of p(x), let p(x) = 0


x3 + x2 — x — 1 = 0


x2 (x + 1) – 1 (x + 1) = 0


(x2 – 1)(x + 1) = 0


(x – 1) (x + 1)(x + 1) = 0 Using the identity: (a2 – b2) = (a – b) (a + b)


x – 1 = 0 or x + 1 = 0 or x + 1 = 0


x = 1 or x = –1 or x = –1


Two distinct zeros of p(x) are 1 and –1.


Hence, p(x) has at the most two distinct zeros.


So the statement is True.


(4) Given, p(x) = x3


To find the zeros of p(x), let p(x) = 0


x3 = 0


x = 0.


The graph of p(x) = x3 meets the X-axis at only one point i.e. (0, 0).


So the statement is True.


(5) If the graph of the quadratic polynomial p(x) does not intersect the x-axis at any point, then the quadratic polynomial does not have any real zero.


So the statement is False.


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