x²+10x+25-9=0（x+5）²-9=0（x+5）²=9 x+5=正负3所以x=-2或者x=-8x²-x-3/4=0x²-x+1/4-1=0(x-1/2)²=1 x-1/2=正负1所以x=-1/2或者x=3/23x²+6x-5=0=3(x+1)²-8(x+1)²=8/3 ...