已知F（X）=0.25X方-1.5X+1.25,求F（2X-1）的解析式.

1.因为F（X）=0.25X方-1.5X+1.25
把2X-1去代X
F(2X-1)=0.25(2X-1)^2-1.5(2X-1)+1.25
F(2X-1)=X^2-4X+3
2.设F(X)=AX^2+BX+C
F(2X)=4AX^2+2BX+C
F(3X+1)=9AX^2+(6A+3B)X+A+B+C
F（2X）+F（3X+1）=13AX^2+(6A+5B)X+A+B+2C=13X^2+6X-1
所以A=1,B=0,C=-1
F(X)=X^2-1