【参考答案】设点M(x,y)则 √[(x+4)²+y²]=2√[(x-2)²+y²]即 (x+4)²+y²=4[(x-2)²+y²]x²+8x+16+y²=4x²-16x+16+4y²3x²-24x+3y²=0x²-8x+y&...