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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