Remove["Global`*"];
a = (p + 1.408/v^2)(v - 0.03913) - 0.083145*120;
sol = Solve[a == 0];
p = p /. sol[[1]];
Plot[{p}, {v, 0.05, 1}];
dpdv = D[p, v];
boundary = Solve[dpdv == 0];
downbound = p /. boundary[[2]];
upbound = p /. boundary[[3]];
Print["The answer is between ", downbound , " and ", upbound];
a = Input["Try vapor pressure"]
verbound = Solve[p == a, v]
leftbound = v /. verbound[[1]]
rightbound = v /. verbound[[3]]
formula = NIntegrate[(a - p), {v, leftbound, rightbound}]
反覆執行上述程式，猜測蒸氣壓並代入至輸出值（水平線減直線的總積分值）趨近零，
答案約為25.981 bar。
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