(a的2次方-6ab+9b的2次方)/(3ab-a的2次方)并求当a/b=2

Question

(a的2次方-6ab+9b的2次方)/(3ab-a的2次方)并求当a/b=2

Answer 1

(a^2-6ab+9b^2)/(3ab-a^2)
=(a-3b)^2/[a*(3b-a)]
=(3b-a)/a
当a/b=2时,
原式=(3-a/b)/(a/b)=(3-2)/2=1/2