bài 3 :tìm x a,4^x+4^x+1=320 b,5^x.5^3=-(15-40) c,2x^2-15=1 d,1762-(4X+3)=-5 e,(x^2+1)(x^2-1)=0

Đáp án:

↓↓

Giải thích các bước giải:

`a)`

`4^x+4^{x+1}=320`

`=>4^x.(1+4)=320`

`=>4^x.5=320`

`=>4^x=64`

`=>4^x=4^3`

`=>x=3`

`b)`

`5^x.5^3=-(15-40)`

`=>5^x.125=25`

`=>5^x=1/5` 

`=>5^x=5^-1`

`=>x=-1`

`c)`

`2x^2-15=1`

`=>2x^2=16`

`=>x^2=4`

`=>x^2=2^2`

`=>x=2`

`d)`

`1762-(4x+3)=-5`

`=>4x+3=1767`

`=>4x=1764`

`=>x=441`

`e)`

`(x^1+1)(x^2-1=0`

`=>x^2-1=0`

`=>x^2=1`

`=>`\(\left[ \begin{array}{l}x=1\\x=-1\end{array} \right.\) 

Vậy \(\left[ \begin{array}{l}x=1\\x=-1\end{array} \right.\)