（x+8）（960-20x）-960x=0,960x-20x²+960×8-160x-960x=0-20x²-160x+7680=0x²+8x-384=0(x²+8x+16)-384-16=0(x+4)²-20²=0(x+4+20)(x+4-20)=0(x+24)(x-16)=0x1=-24,x2=16