设M=4x^2-12x+9y^2+30y+35 则 A.M>0 B.M≥0 C.M<0 D.M≤0
问题描述:
设M=4x^2-12x+9y^2+30y+35 则 A.M>0 B.M≥0 C.M<0 D.M≤0
答
M=4x^2-12x+9y^2+30y+35
=4x^2-12x+9+9y^2+30y+25+1
=(2x-3)²+(3y+5)²+1
≥1
选择A