If the roots of the equation a(b – c)x2 + b(c – a)x + c(a – b) = 0 are equal, then which of the following is true?

• b = ( a + c)/ ac
• 2/ b = (1/ a) + (1/ c)
• 2 b = (1/ a) + (1/ c)
• abc = ab + bc + ca