n^2-18n+42

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n^2-18n+42n^2-18n+42n^2-18n+42n²-18n+42n²-18n+81(n-9)²-√399-√39n²-8n+42n²-8

n^2-18n+42
n^2-18n+42<0 怎么解

n^2-18n+42
n²-18n+42<0
n²-18n+81<39
(n-9)²<39
-√399-√39

n²-8n+42<0
n²-8n+16<-42+16
(n-4)²<-26
此不等式无解。

n^2-18n+42<0
n^2-18n+81-39<0
n^2-18n+81<39
(n-9)²<39
-√399-√39