The answers are -1, 0,2, 3 right?
$$a*b =\frac{1}{a} + \frac{1}{b} Hence: a*b = (a+b)/(a x b) a+b = 9 , a x b = 20 a*b = 0.45$$
$$Sn = \frac{(a1+an)*n}{2} S = the sum of the numbers a1 = first number an = last number n = quantity of numbers an = a1 + d(n-1) [d = 1 = the common difference of successive members) 201 = 101 - 1(n-1) n = 101 S101 = [(101+201)*101]/2 S101 = 15251$$
$$\frac{a^{2}}{4} + \frac{a^{2}}{4} = 2*\frac{a^{2}}{4} = \frac{a^{2}}{2}$$
