C-11-Q047mediumsingle_mcqa+ba−b=k\dfrac{a+b}{a-b}=ka−ba+b=k হলে a:b=?a:b = ?a:b=?a(k+1):(k−1)(k+1):(k-1)(k+1):(k−1)b(k−1):(k+1)(k-1):(k+1)