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Question 84
The zeros of the cubic polynomial $$2x^3 - x^2 - 2x + 1$$ are $$a, b$$ and $$c$$ respectively. Find $$ab + bc + ca$$ =?
Solution
by hit and trail one zero is 1,
$$\ 2x^3-2x^2+x^2-x+1=0$$
$$2x^2$$(x-1)+x(x-1)-1(x-1)=0
(x-1)($$2x^2+x-1$$)=0
zero are 1,-2 and 1, which is the value of a,b,c
so ab+bc+ca= -1
Hence option 'D' is correct.
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