3.已知x方+x-1=0,求x三方+2x方+3的值 4.分解因式x方+7x-18=? 5.多项式x方-4,x方-7X+10,x方-4x+4的公因式? 6.诺x方+4x+y方-6y+13=0,则x,y各个值是? 7.