Question

化简求值，要详细过程[(y-2x)(-2x-y)-4(x-2y)²]÷3y,其中x=1,y=-3

化简求值，要详细过程[(y-2x)(-2x-y)-4(x-2y)²]÷3y,其中x=1,y=-3
a²(a+1)²-2(a²-2a+4)，其中a=-2

Answer 1

[(y-2x)(-2x-y)-4(x-2y)²]÷3y
=[4x^2-y^2-4x^2+16xy-16y^2]/3y
=[16xy-17y^2]/3y
=16x/3-17y/3
希望你能看懂，祝你学习进步

追问

a²(a+1)²-2(a²-2a+4)，其中a=-2，这个呢？谢谢

追答

a²(a+1)²-2(a²-2a+4)
=a^2(a^2+2a+1)-2a^2+4a-8
=a^4+2a^3+a^2-2a^2+4a-8
=a^4+2a^3-a^2+4a-8
=2^4+2*2^3-2^2+4*2-8
=16+16-4+8-8
=28

追问

这道题有一点小问题，最后结果不是28，是-20.不过还是谢谢你

Answer 2

[(y-2x)(-2x-y)-4(x-2y)²]÷3y
=[-(y-2x)(2x+y)-4(x-2y)²]÷3y
=[(2x-y)(2x+y)-4(x-2y)²]÷3y
=[4x^2-y^2-4(x-2y)²]÷3y
=[4-9-4*7^2]]÷(-9)
=67/3
a²(a+1)²-2(a²-2a+4)
=a²(a+1)²-2(a-2)²
=4*1-2*4^2=4-32=-24