(2)x²-x-7/4=0x²-x=7/4(x-1/2)²-1/4=7/4(x-1/2)²=2x-1/2=±√2x=(1±2√ 2)/2(4)4x²-6x-3=0x²-3/2x=3/4(x-3/4)²-9/16=3/4(x-3/2)²=21/16x-3/2=±√21/4x=(6±√21)/4(5)x(x+4)=8x+12x²+4x=8x+12x²-4x-12=0(x+2)(x-6)=0x=-2或 x=6
照片太模糊了。