Hello, I need some help for this question please.

\f\"When an electric current passes through two resistors with resistance n and [ r2, connected in parallel, the combined resistance, R, is determined by the equation 1 1 1 u _=_ _ , (l R T1+T2 (R>O,T1>0,T2>0) Assume that T2 is constant, but an changes. 1. Find the expression for R through 1"; and r; and demonstrate that R is an increasing function of 1*]. You do not need to use derivative, give your analysis in words. Hint: a simple manipulation with the formula R = which you derive, will convert R to a form, from where the answer is clear. or you can analyze {*) as it is. 2. Make a sketch of R versus an (show 1-2 in the sketch). What is the practical value of R when the value of T1 is very large? Question 7. If you have 100 meters of fencing and want to enclose a rectangular area up against a. long, straight wall, what is the largest area you can enclose