(1)2x^2-xy-4y^2; 无法有理数因式分解,请检查是不是写错了.非要因式分解的话只能是无理数因式分2x^2-xy-4y^2=2(x^2-(1/2)yx)-4y^2=2{[x-(1/4)y]^2-(1/16)y^2}-4y^2=2[x-(1/4)y]^2-(33/8)y^2={√2[x-(1/4)y]-[√(33/8...