If (3a +6b +c +2d) x (3a - 6b - c +2d) = (3a - 6b +c- 2d) x (3a +6b - c- 2d), then which one of the following is correct ?

If bc + cd = 2bd and a + c = 2b, then which one of the following is correct?

If 2^(x−1) + 2^(x+1) = 1280, then the value of x²+9x is

If x + (1/y) = 1 and y + (1/z) = 1, then the value of z + (1/x) is

If z = x + iy is a complex number such that iz = 2 + 3i, then the value of x − y is

If a, b, c, d, e and f satisfy 2a = 3b = 6c = 9d = 12e = 18f, then what is the value of (a + b)/(c + d + e + f)?