Question

已知实数X,Y满足X2+3X+2Y-3=0,则X+Y的最大值是

Answer 1

设k=x+y,y=k-x代入x^2+3x+2y-3=0

x^2+3x+2(k-x)-3=0

x^2+x+2k-3=0

判别式=1-4(2k-3)>=0

1-8k+12>=0

k