a = 10-b (10-b)/x+b/y=1 1-(10-b)/x = b/y y = bx/(x+b-10) > 18-x bx > (18-x)(x+b-10) = 18x+18b-180-x2-xb+10x = -x2+(28-b)x+18(b-10) x2+(2b-28)x+18(10-b) > 0 ==> (2b-28)2-4*18(10-b) b2-28b+196 - 180+18b b2-10b+16 (b-5)(b-5) b-5 b<8 ????......
因为a/x+b/y=1,所以x+y=(x+y)(a/x+b/y)=a+b+bx/y+ay/x=10+bx/y+ay/x 又因为bx/y+ay/x≥2√(bx/y)(ay/x)=2√(ab),当且仅当bx/y=ay/x时成立 x+y最小值为10+2√(ab)=18,所以ab=16,又因为a+b=10,所以a=2,b=8或a=8,b=2
答：设定点为A(-a,0),B(a,0),动点为M(x,y). 依题意,动点M与定点A;的距离的比是L,所以|MA|=L|MB|.依题意显然有L>0. --->(x...详情>>
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