Write each polynomial below as a product of first degree polynomials. Write also the solutions of the equation p(x) = 0 in each.
p(x) = 2x2 – 5x + 2
Given, p(x) = 2x2 – 5x + 2
Now, we need to write the given polynomial as a product of first degree polynomial and p(x) = 0
⇒ 2x2 – 5x + 2 can be written as 2(x2 –
x + 1)
⇒ Now, we will find out the factors for x2 –
x + 1
⇒ x2 –
x + 1 is in the form x2 – (a + b)x + ab and (x – a)(x – b) are the factors
∴ coefficient on either side of the polynomial is same and a + b = ![]()
and ab = 1
⇒ we know that (a + b)2 –(a – b)2 = 4ab
∴ (a + b)2 – 4ab = (a – b)2
⇒
– 4(1) = (a – b)2
⇒
– 4 = (a – b)2
⇒
= (a – b)2
⇒
= (a – b)2
⇒ a – b = ![]()
⇒ a – b = ![]()
⇒ We need to find out the values of a and b by solving (a + b) + (a – b) and (a + b) – (a – b)
⇒ we take a – b = ![]()
⇒ (a + b) + (a – b) =
+ ![]()
⇒ 2a = ![]()
⇒ a = 2
⇒ (a + b) – (a – b) =
– ![]()
⇒ 2b = ![]()
⇒ b = ![]()
∴ we get a = 2 and b = ![]()
And if we take a – b = –
we get as follows
⇒ (a + b) + (a – b) =
+ (–
)
⇒ 2a = ![]()
⇒ a = ![]()
⇒ (a + b) – (a – b) =
– ![]()
⇒ 2b = ![]()
⇒ b = 2
∴ a =
and b = 2
⇒ So, we have 2(x –
)(x – 2)
⇒ (2x – 1)(x – 2)
∴ (2x – 1)(x – 2) are the factors
⇒ p(x) = 0 if (2x – 1) is 0 and (x – 2) is 0
⇒ (2x – 1) = 0
⇒ 2x = 1
⇒ x = ![]()
⇒ Substitute, x =
in 2x2 – 5x + 2 = 2(
2 – 5(
+ 2 =
–
+ 2 = 0
⇒ (x – 2) = 0
⇒ x = 2 substitute, 2x2 – 5x + 2 = 2(2)2 – 5(2) + 2 = 8 – 10 + 2 = 0
Hence, (2x – 1)(x – 2) are the first degree factors of the polynomial and
and 2 are the solution of the given polynomial 2x2 – 5x + 2
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