Question

6.8^x-1+8^x+1=6.8^19+8^21

 

Answer 1

Trường hợp 1: 6.8^x-1=6.8^21

x-1=19

x=19+1

x=20

vậy x=20

Trương hợp 2: 8^x+1=8^21

x+1=21

x=21-1

x=20

vậy x=20

Answer 2

6.8^x-1+8^x+1=6.8^19+8^21

<>6.8^x-1+8^x-1.8^2=6.8^19+8^19.8^2

 <>8^x-1(6+8^2)=8^19(6+8^2)

<>8^x-1=8^19

<>x-1=19

<>x=19+1=20