Question

[Phạm Bùi Quang Huy]

tìm x,y:2^x= 4^y-1 và 27^y = 3^x+8

Answer 1

[Lê Chí Cường]

Ta có:2^x=4^y-1=>2^x=(2²)^y-1=2^2.(y-1)

=>x=2.(y-1)

=>3x=6.(y-1)

          27^y=3^x+8=>27^y=3^x+5.3³=3^x+5.27=>27^y:27=27^y-1=3^x+5=>(3³)^y-1=3^x+5=>3^3.(y-1)=3^x+5

=>3.(y-1)=x+5

=>6.(y-1)=2x+10=3x

=>2x+10=3x

=>3x-2x=10

=>x=10

=>y=10:2+1=6

Vậy x=10, y=6

Answer 2

[viet]

le chi cuong lam sai roi