Question

SOS!因式分解⒈已知：x^2+xy+y=14① y^2+xy+x=28② 求XY的值．⒉x、y为正整数,2x^2+3y

Answer 1

1.两式相加,相减得到x=1.6 y=4.4 xy=7.04

2.2x^2+3y^2=4x^2y^2+1

2x^2+3y^2-4x^2y^2-1=0 (1)

y^2=（1-2x^2）/(3-4x^2)>=0

因为x为正整数得到x^2>=0.75或x^2=1

再由（1）式可得x^2=（1-3y^2)/(2-4y^2)>=1

得到(y^2-1)/(2-4y^2)>=0

所以0.5