If α & β are zeroes of , find the polynomial whose zeroes are 2α + 3β and 3α + 2β.
Answers
QUESTION :-
If α & β are zeroes of 2x²- 5x + 7, find the polynomial whose zeroes are 2α + 3β and 3α + 2β.
SOLUTION :-
➠ p(x) = 2x²-5x+7 -----(given)
➠ let, the two zeroes be α & β.
➠ .°. sum of zeroes = α + β
➠ (-b)/ a = -(-5)/2 = 5/2-------(1)
➠ .°. product of zeroes = αβ
➠ c /a = 7/2 ------------(2)
➠ zeroes of polynomial are (2α+3β) and (3α+2β) .
➠ since, α + β = (2α + 3β) + (3α + 2β)
➠ 5α + 5β = 5(α+β)
➠ from (1) , we get
➠ 5(α+β) = 5×5/2 = 25/2.
➠ .°. α + β = 25/2.
➠ αβ = (2α +3β)(3α +2β)
➠ αβ = 6α² +4αβ + 9αβ + 6β²
➠ αβ = 6(α²+β²) +13αβ
➠ αβ = 6[(α+β)² -2αβ] -13αβ
➠ αβ = 6[(5/2)² - 2(7/2)] + 13 * 7/2 ----[from (1) & (2)]
➠ αβ = 6[25/4 -7] +91/2
➠ αβ = 6*(-3)/4 + 91/2 = -9/2 + 91/2 = 82/2 = 41
➠ .°. αβ = 41.
therefore, the polynomial obtained is.
➠ g(x)= x²-(α+β)x + αβ
➠ .°. g(x) = x² - (25/2)x + 41.
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