. If a and b are real numbers between 0 and 1
such that the points (a, 1), (1,b) and (0,0) form an equilateral triangle, then 2(a + b) – ab is equal to
Sol: The given vertices are P(a,1), Q(1, b) and R(0,0) and the triangle is equilateral. Hence apply the conditions that angle between PR and RQ should be 600 and QP = PR.
Hence (A) is the correct answer