化简 求值、
(1\2x+13\y)² -(1\3x-1\2)² -(5\6x+5\6y)(1\6x-1\6y)
其中2的十次方=x²=4的Y次方
化简 求值、
(1\2x+13\y)² -(1\3x-1\2)² -(5\6x+5\6y)(1\6x-1\6y)
其中2的十次方=x²=4的Y次方
解:(1/2x+1/3y)² -(1/3x-1/2y)² -(5/6x+5/6y)(1/6x-1/6y)
=[(1/2x+1/3y)+(1/3x-1/2y)][(1/2x+1/3y)-(1/3x-1/2y)]-5/36(x+y)(x-y)
=(5/6x-1/6y)(1/6x+5/6y)-5/36(x²-y²)
=5/36x²+25/36xy-1/36xy-5/36y²-5/36(x²-y²)
=2/3xy
因为2^10=x²,所以x²=(2^5)²,即x=32
又因为2^10=4^y,所以(2)^2y=2^10,2y=10,即y=5
当x=32,y=5时,原式=2/3×32×5=320/3