c = 0.5
\[Alpha] = 0.9
d = 4
k = 4
\[Beta] = (
d (4 - \[Alpha]) (\[Alpha] - 2) +
4 [3 w + c (\[Alpha] - k)] - \[Alpha] (c k + w - \[Alpha]))/(
c k (4 - 3 \[Alpha]))
Plot[(2 w + \[Alpha] (1 + c) +
2 k c (\[Beta] - 1))/(\[Alpha] (4 - \[Alpha])), {w, 3.7, 4.8}]

有人吗救救孩子啊

改成这样
\[Beta] = (d (4 - \[Alpha]) (\[Alpha] - 2) +
4 (3 w + c (\[Alpha] - k)) - \[Alpha] (c k +
w - \[Alpha]))/(c k (4 - 3 \[Alpha]))
注意圆括号用来确定优先计算,方括号内只能是函数的自变量,花括号内是集合的元素