Tìm n∈Z biết :

a,27ⁿ/3ⁿ

^b,\(\frac{25}{5^n}\)=5

c,\(\frac{81}{\left(-3\right)^n}=-243\)

d,\(\frac{1}{2}\cdot2^n+4\cdot2^n=9\cdot2^5\)

e,(\(\frac{1}{3}\))ⁿ=\(\frac{1}{81}\)

f,\(\left(\frac{-3}{4}\right)^n=\frac{81}{256}\)

g,\(\frac{-512}{343}=\left(\frac{-8}{7}\right)^n\)

h,5^-1*25ⁿ=125

k,3^-1*3ⁿ+6*3^n-1=7*3⁶

TÌM x∈Q BIẾT :

a,(x-\(\frac{1}{2}\))=0

b,(x-2)²=1

c,(x-2)³=-8

d,(x+\(\frac{1}{2}\))²=\(\frac{1}{16}\)

e,(3x+1)³=-27

cho hình vẽ bên .chứng minhAB//CD