#1, x , y are real number, x>=y>=1, 2*x^2-xy-5x+y+4=0,then x+y=?
#2,look at the Attach image,ABCD is a square,and EFGH is a quadrangle,
angle BEG and angle CFH are both sharp angles. EG=3(units),FH=4(units),
the acreage of EFGH is 5, question: what is the acreage of ABCD?
#3 the...