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Let `f(x) =ax^2 + bx+ c AA a, b, c in R, a != 0` satisfying `f (1) + f(2)=0`. Then, the quadratic equation `f(x)=0` must have :A. no real rootB. 1 and 2 as real rootsC. two equal rootsD. two distinct real roots |
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Answer» Correct Answer - D We have, `f(x) = ax^(2) + bx + c` `therefore" "f(1) + f(2) = 0 rArr 5a + 3b + 2c - 0` Let D be the discriminant of f(x) = 0. Then, `D = b^(2) - 4ac` `rArr" "D=((5a+2c)/(-3))^(2)-4ac" "["Using (i)"]` `rArr" "D=((5a+2c)^(2)-36ac)/(9)` `rArr" "D=(25a^(2)+4c^(2)-16ac)/(9)=(1)/(9){(4a-2c)^(2)+9a^(2)} gt 0` Hence, f(x) = 0 has two distinct real roots. |
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