原式=(4x²-y²)(x²-y²+3x²)=(4x²-y²)²则(4x²-k²x²)²=x^4(4-k²)²*x^4=x^4所以(4-k²)²=14-k²=±1k²=3或5所以k=-√5，k=√5，k=-√3，k=√3
