ai dc ng do la ng thong minh vi day la bai toan cho hoc sinh gioi toan [chu y:day chi la dang toan loai kha thui nha]
tim x
3^x =81
2^x+3 +2^x=144
x^2 - 4x=0
thc hien phep tinh
(5^4 + 4^7) (8^9-2^7) (2^4 - 4^2)
4^3.51+4^3.49+2.(3^2 +4^2 )
tim n,biet
3^n+3 + 3^n =252
z thui phai giai het moi chon nha chi dc sai 2 cau la toi da
a) vì 81=34=(-3)4
=> x=3
hoặc x=-3
b) 2^x+3 +2^x=144
=> 2x.23+2x=144
=>2x.(23+1)=144
=>2x.9=144
=>2x=144:9=16
mà 16=24
=> x=4
c)x2-4x=0
=>x.(x-4)=0
=> x=0
hoặc x-4=0 => x=4
=> x=0
hoặc x=4
d)(5^4 + 4^7) (8^9-2^7) (2^4 - 4^2)
=(5^4 + 4^7) (8^9-2^7) .(16-16)
=(5^4 + 4^7) (8^9-2^7) .0
=0
e)4^3.51+4^3.49+2.(3^2 +4^2 )
=43.(51+49)+2.(9+16)
=64.100+2.25
=6400+50
=6450
f)3n+3+3n=252
3n.33+3n=252
3n.(33+1)=252
3n.28=252
=>3n=252:28=9
mà 9=32
=>x=2
