If α and β are zeros of the poly x²+4x +1 ,Without finding zeros Find α and β
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Answers
If α & β are zeroes of f(x) =x²-x-2
then
α + β = -b/a = 1
α β = c/a = -2
let α’ =2α+1 & β’ = 2β+1
α’ + β’ = 2α+1 + 2β+1
=2α+2β+2 =2(α+β)+2 =2(1)+2=4
α’ β’=(2α+1)(2β+1) = 4α β+2α+ 2β+1 = 4(-2)+2(1)+1=-8+2+1=-5
Polynomial having α’ & β’ as zeroes is given by
k (x²-(α’ + β’)x +α’ β’)
= k (x² - 4x -5) Answer
By giving different values to k, there can be infinite polynomials
Given,
- x² + 4x + 1
To find,
- Find α and β
Solution,
Let P(x) = x² - 4x - 8
Zero of polynomial is the value of x where P(x) =0
Putting P(x) = 0
- x² - 4x - 8 = 0
We find roots using splitting the middle term method
Splitting the middle term method We need to find two numbers where
- Splitting the middle term method We need to find two numbers whereSum = - 4
- Product = -8 × 1= - 8
x² - 4x + 2x - 8 = 0
x - 8 = 0x(x - 2) + 4(x - 4 ) = 0
( x + 2 ) ( x - 4 ) = 0
4 ) = 0So x = 2, - 4
Therefore, α=- 2 & β = - 4 are the zeroes of the polynomial
P(x) = x² - 4x - 8
= x² - 4x - 8
Comparing with a ² + bx + c
So, a = 1, b = - 4, C = - 8
We verify
- Sum of zeroes = coefficient of x / coefficient of x²
I.e α + β = - 1/α
LHS = RHS
= α + β = - b/a
= α + β = - b/a
= - 2 + 4 = - 4/1
= 4 = 4
- Product of zeroes = coefficient of x / coefficient of x²
I.e α × β = c/a
LHS = RHS
α β = c/a
(-2)(4)= - 8/1
-8= - 8
Since, RHS = LHS