Determine the truth values of the following statements (assuming that x and y are real numbers)?
a) the product xy = 0 if and only if either x = 0 or y = 0.
b) The sum of squares x²+y² >1iff both x and y are greater than 1.
c) x² −4x+3−0⇔x=3.
d) x² >y² ⇔x>y.