已知点P（﹣2，3）关于原点的对称点为M（a，b），则a+b=____ ．

阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。

    All scientists subscribe ____ the view that it is human activities that have caused the global warming. Huge ____ (quantity) of carbon dioxide produced by burning fuels like coal,  natural gas and oil ____ (result) in the "greenhouse effect". All scientists also agree that the levels of carbon dioxide keep on ____ (increase), so more heat energy tends to be ____ (trap) in the atmosphere. ____ the scientists have different attitudes towards this phenomenon. On the one hand, some think the ____ of increasing the temperature by 5 degrees would be a catastrophe. On the other hand, others are ____ to this view and believe that there will be few bad environmental ____ caused by more carbon dioxide. On the contrary, they think it will be beneficial to plants, crops and a greater range of animals, ____ will make people's life better.

对于方程（x﹣1）（x﹣2）=x﹣2，下面给出的说法不正确的是（　　）

大约两千四百年前，我国的学者墨翟和它的学生做了世界上第一个小孔成像的实验，解释了小孔成像的原理。小光同学将两个长度均为50cm，直径为5cm的直筒套在一起，做成如图的仪器(M筒的直径稍大，可以在N筒上并能前后移动)。