Question: When an electric current passes through two resistors with resistance r1 and r2, connected in parallel, the combined resistance, R, can be calculated from the equation
(1/R) = (1/r1) + (1/r2),
Where R, r1, and r2 are positive. Assume that r2 is constant.
(a) Show that R is an increasing function of r1.
(b) Where on the interval a ≤ r1 ≤ b does R take its maximum value?