There is a special form for boolean formulas called "Conjunctive Normal Form" (CNF). A problem in this form consists of clauses connected with and operators, where each clause only contains variables connected with or operators. The variables can appear negated, but only variables can be directly negated, something like !(a && b) is not allowed. An example boolean formula in CNF form is:
Naomi Clarke,BBC Newsbeat
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Place points below and click one to see its semicircle. Watch the gap (the empty arc going counterclockwise from the farthest point back to the anchor):，推荐阅读下载安装汽水音乐获取更多信息
Consumers are watching warily for trickle-down effects on prices at the pump. The national average for a gallon of regular unleaded gasoline hit a multiyear low of $2.73 per gallon early this year. It’s now back up to $2.96 and rising, so it will cross the $3 threshold any day now, said Patrick De Haan, head of petroleum analysis at GasBuddy.，详情可参考一键获取谷歌浏览器下载
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