Question

小李在电脑中设置了一个有理数的运算程序，输入数a，输入*键，再输入b,得到运算a*b=a2-2(3a-1/b)÷(a-b)求

小李在电脑中设置了一个有理数的运算程序，输入数a，输入*键，再输入b,得到运算a*b=a2-2(3a-1/b)÷(a-b)求(-1/2)*2

Answer 1

(-1/2)²-2[3(-1/2)-1/2]÷[(-1/2)-2]
=1/4-2×-2÷(-5/2)
=1/4+4×(-2/5)
=1/4-8/5
=5/20-32/5
=-27/5

Answer 2

a=-1/2,b=2代入得
(-1/2)*2
=(-1/2)^2-2[3*(-1/2)-1/2]÷(-1/2-2)
=1/4-2(-3/2-1/2)÷(-1/2-2)
=1/4-2*(-2)÷(-5/2)
=1/4-8/5
=-27/20

Answer 3

解：（－1/2）*2＝（－1/2）²－2×〔3×（－1/2）－1/2〕÷（－1/2－2）＝1/4－2×（－2）÷（－5/2）＝1/4＋4×（－2/5）＝1/4－8/5＝5/20－32/20＝－27/20

Answer 4

解：（－1/2）*2＝（－1/2）²－2×〔3×（－1/2）－1/2〕÷（－1/2－2）＝1/4－2×（－2）÷（－5/2）＝1/4＋4×（－2/5）＝1/4－8/5＝5/20－32/20＝－27/20

Answer 5

解：原式=1/4-2×(-5/2)/(5/2)
=1/4+2
=9/4