Giúp mik `3` câu này nha Tìm `x` ạ

a) `3^(-1) .4^x+3. 4^x=5/3 .2^7`

`⇒ 4^x .(3^(-1) +3)=5/3 .128`

`⇒ 4^x . 10/3=640/3`

`⇒ 4^x =640/3÷10/3=64`

`⇒ 4^x=4^3`

`⇒ x=3`

b) `9^(-x) .27^x=243`

`⇒ 3^(-2x) .3^(3x)=243`

`⇒ 3^(-2x+3x)=243`

`⇒ 3^x=3^5`

`⇒ x=5`

c) `2^(-2) .2^x+2. 2^x=9.2^6`

`⇒ 2^x .(2^(-2) +2)=9.64`

`⇒ 2^x . 9/4=576`

`⇒ 2^x=576÷9/4`

`⇒ 2^x=256`

`⇒ 2^x=2^8`

`⇒ x=8`