计算题 一道解不等式 一道先化简再求值7减x小于等于1减4乘(x减3)(m+2/m²-2m -1/m-2)÷2/m²-4,其中m= -1/2
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计算题 一道解不等式 一道先化简再求值7减x小于等于1减4乘(x减3)(m+2/m²-2m -1/m-2)÷2/m²-4,其中m= -1/2
计算题 一道解不等式 一道先化简再求值
7减x小于等于1减4乘(x减3)
(m+2/m²-2m -1/m-2)÷2/m²-4,其中m= -1/2
计算题 一道解不等式 一道先化简再求值7减x小于等于1减4乘(x减3)(m+2/m²-2m -1/m-2)÷2/m²-4,其中m= -1/2
7-x≤1-4*(x-3)
7-x≤1-4x+12
3x≤6
x≤2
(m+2/m²-2m -1/m-2)÷2/m²-4,其中m= -1/2
(m+2/m²-2m -1/m-2)÷2/m²-4
=m+2/m²-2m*(m^2-4)/2-1/m-2*(m^2-4)/2
=(m+2)^2/2m-(m+2)/2
=(m+2)【(m+2)/2m-1/2】
=3/2*(-3/2-1/2)
=-3
7-x ≤ 1-4(x-3)
7-x ≤ 1-4x+12
7-x ≤ 13-4x
-x +4x ≤ 13-7
3x ≤ 6
x ≤ 2
[(m+2)/(m²-2m) - 1/(m-2)] ÷ 2/(m²-4)
= [(m+2)/(m²-2m) - m/(m²-2m)] ÷ ...
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7-x ≤ 1-4(x-3)
7-x ≤ 1-4x+12
7-x ≤ 13-4x
-x +4x ≤ 13-7
3x ≤ 6
x ≤ 2
[(m+2)/(m²-2m) - 1/(m-2)] ÷ 2/(m²-4)
= [(m+2)/(m²-2m) - m/(m²-2m)] ÷ 2/(m²-4)
= 2/(m²-2m) × (m²-4)/2
= (m²-4)/(m²-2m)
= (m+2)(m-2) / [m(m-2)]
= (m+2) / m
把 m = -1/2 代入,得
原式
= (2-1/2) /(-1/2)
= - 3
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