JEE Advanced 2020 Mathematics question
Suppose denote the distinct real roots of the quadratic polynomial and suppose denote the distinct complex roots of the quadratic polynomial . Then the value of
ac(a-c) + ad(a-d) + bc(b-c) + bd(b-d)
is
Answer: (D)
Solution
Expand and regroup: ac(a-c)+ad(a-d)+bc(b-c)+bd(b-d) = a^2(c+d) - a(c^2+d^2) + b^2(c+d) - b(c^2+d^2) = (a^2+b^2)(c+d) - (a+b)(c^2+d^2). From : , , so $+ = 400 +
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