Solve 1/C=1/C1+1/C2 for C1.

Answer 1

Subtract 1/C2 from each side.

1/C1 = 1/C - 1/C2 = (C2-C)/(C*C2)

Now turn both fractions upside down. This is called "taking the reciprocal of both sides"

C1 = C*C2/(C2 - C) = 1/[(1/C) - (1/C2)]

Answer 2

(C+1)(c2_c+)