2a^x-2ax+1/2x=
(x+1)(2x-3)+2(x+1)(3-2x)+(x+1)^2 (2x-3)=
3xy-9x^2-1/4y^2=
说明3^24-1能被28整除
有过程谢谢!
2a^x-2ax+1/2x=
(x+1)(2x-3)+2(x+1)(3-2x)+(x+1)^2 (2x-3)=
3xy-9x^2-1/4y^2=
说明3^24-1能被28整除
有过程谢谢!
3^24-1=(3^12+1)(3^12-1)=(3^12+1)(3^6+1)(3^6-1)=(3^12+1)(3^6+1)(3^3+1)(3^3-1)=(3^12+1)(3^6+1)(3^3-1)*28
所以3^24-1能被28整除
3xy-9x^2-1/4y^2=-(3x+1/2y)^2
(x+1)(2x-3)+2(x+1)(3-2x)+(x+1)^2 (2x-3)=(x+1)(2x-3+6-4x+2x^2-x-3)=(x+1)(2x^2-3x+3)
3xy-9x^2-1/4y^2= -(9x^2+1/4y^2-3xy)
= -[(3x)^2+(1/2y)^2-3xy]
= - (3x-1/2y)^2 (用安全平方差公式分解)
解:(x+1)(2x-3)+2(x+1)(3-2x)+(x+1)^2 (2x-3)=(x+1)(2x-3+6-4x+x^2+2x+1)=(x+1)(x^2+4)
3^24-1=(3^12)^2-1=(3^12+1)(3^12-1)=(3^12+1)(531441-1)=(3^12+1)×531440=(3^12+1)×18980×28所以能被28整除