某同学在做酸碱中和反应的实验时,向NaOH溶液中滴加盐酸时产生了气泡,由此得出了NaOH溶液已变质的结论.并对该变质的NaOH溶液开展了以下探究:
【提出问题】该NaOH溶液是全部变质还是部分变质呢?
【猜想与假设】
猜想1:NaOH溶液部分变质.
猜想2:NaOH溶液全部变质.
【查阅资料】CaCl2溶液呈中性.
Hi! I'm Alice.
一元二次方程x2-5x-6=0的根是( )
如图,在图1中,互不重叠的三角形共有4个,在图2中,互不重叠的三角形共有7个,在图3中,互不重叠的三角形共有10个,…,则在第n个图形中,互不重叠的三角形共有个____(用含n的代数式表示).
根据句意及汉语提示完成单词.
① Have you____ (曾经)taken the subway alone late at night?
②She won first____ (奖)in the 100-meter race.
③It was his____ (梦想)to play football for his country.
④We can not____ (付得起)the cost of two telephones.
⑤It was a____ (遗憾)that you missed the party.