化简求值:[(x+2y)(x-2y)-(x+4y)²]÷(4y),其中x=√2/2,y=-[(3√2)/5].

问题描述:

化简求值:[(x+2y)(x-2y)-(x+4y)²]÷(4y),其中x=√2/2,y=-[(3√2)/5].

原式=(x²-4y²-x²-8xy-16y²)÷4y
=(-8xy-20y²)÷4y
=-2x-5y
=-√2+3√2
=2√2