(d) Still assuming the parallelogram law, show that for any a a € R, ||ax + y||²||ax - y||² = a(||x + y||² − ||x – y||²). (Hint. For a € N, this follows from part (c) by induction. Show it next for reciprocals of natural numbers, a = 1/n, then for (positive) rational numbers. Use continuity to conclude it is true for all a > 0, then deal with a ≤ 0.) Cu

(4) Indicate whether each statement is True (T) or False (F). If T, prove it directly. If F, provide a counterexample (a) Va, b e Z, if a? = b² then a = (b) Vm E Z, if m> 2 then m² - 4 is composite (c) The difference of any two odd integers is even (d) The sum of any two rational numbers is a rational number (e) Va, b,c e Z, if a[b · c then a|b or alc (f) Va, b, c E Z, if a|b and b|c then alc (g) Va,b,c E Z, if a|b and alc then a|(b+c) b

3. Which real number is not in the domain of f(x) = √ x + 1(a) -2 (b) -1 (d) 0 (d) 1

I am having a few problems following this book. If someone could please help me with this particular item it would be very helpful.