先化简再求值 [(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]除以(-2y) 其中x=负1/5,y=1/4

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先化简再求值 [(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]除以(-2y) 其中x=负1/5,y=1/4
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先化简再求值 [(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]除以(-2y) 其中x=负1/5,y=1/4
先化简再求值 [(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]除以(-2y) 其中x=负1/5,y=1/4

先化简再求值 [(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]除以(-2y) 其中x=负1/5,y=1/4

原式

= [(4x)²-(3y)²-(16x²+10xy-40xy-25y²)]÷(-2y) 

= (16x²-9y²-16x²+30xy+25y²)÷(-2y) 

= (30xy+16y²)÷(-2y) 

=2y(15x+8y)÷(-2y) 

=-(15x+8y)

=-[15×(-1/5)+8×1/4]

=-(-3+2)

=1

[(4x-3y)(4x+3y)-(2x-5y)(8x+5y)]÷(-2y)
= [(16x²-9y²)-(16x²-30xy-25y²)]÷(-2y)
= (16x²-9y²-16x²+30xy+25y²)÷(-2y)
= (16y²+30xy)÷(-2y)
= 2y(8y+15x)÷(-2y)
= -(8y+15x)
=-15x-8y
=-15*(-1/5)-8*1/4
=3-2
=1