If α and β are the zeroes of the polynomial 5x2– 7x + ...
We have 2 find (1/α + 1/β)
now 1/α + 1/β = (α + β)/ α β (taking LCM)
now by the given poly. we get
(α + β) = -b/a = 7/5
α β = c/a = 2/5
so, (α + β)/ α β = (7/5) / (2/5)
= 7/2
So, 1/α + 1/β = (α + β)/ α β = 7/2
Hence, 1/α + 1/β = 7/2
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If α and β are the zeroes of the polynomial 5x2– 7x + ...
1/α +1/β=α+β/αβ α+β=7/5 αβ=2/5 So, α+β/αβ= 7/2 Therefore the correct option is D
If α and β are the zeroes of the polynomial 5x2– 7x + ...
Given information:
- The polynomial is 5x^2 + 7x + 2.
- The zeroes of the polynomial are α and β.
To find the sum of their reciprocals, we need to find the values of 1/α and 1/β.
Using the zero product property, we know that if α and β are zeroes of the polynomial, then (x - α) and (x - β) are factors of the polynomial.
So, we can write the polynomial as:
5x^2 + 7x + 2 = 0
(x - α)(x - β) = 0
Expanding the above expression, we get:
x^2 - (α + β)x + αβ = 0
Comparing the coefficients of the terms on both sides, we can equate them.
Coefficient of x^2: 1 = 5
Coefficient of x: -(α + β) = 7
Constant term: αβ = 2
We are given that the zeroes are α and β, so we can write:
α + β = -7 (Equation 1)
αβ = 2 (Equation 2)
To find 1/α and 1/β, we can take the reciprocal of both sides of Equation 1 and Equation 2.
Reciprocating Equation 1, we get:
1/(α + β) = -1/7
Reciprocating Equation 2, we get:
1/(αβ) = 1/2
So, 1/α + 1/β = -1/7 + 1/2
To add these fractions, we need to find their least common denominator (LCD), which is 14.
Multiplying the numerator and denominator of -1/7 by 2, we get -2/14.
So, -1/7 + 1/2 = -2/14 + 7/14 = (7 - 2)/14 = 5/14
Therefore, 1/α + 1/β = 5/14.
But we need to find the sum of α and β, not their reciprocals.
Recall Equation 1: α + β = -7
So, we need to find 1/(-7).
Taking the reciprocal, we get -1/7.
Therefore, 1/α + 1/β = 5/14 and α + β = -7.
So, the correct answer is option D) 7/2.