分析:(1)根據(jù)有理數(shù)加法法則同號(hào)相加,取相同符號(hào),并把絕對(duì)值相加;
(2)由題意,取絕對(duì)值較大的加數(shù)-9的負(fù)號(hào),并用較大的絕對(duì)值9減去較小的絕對(duì)值7;
(3)根據(jù)有理數(shù)乘法的運(yùn)算方法,依據(jù)法則是:同號(hào)兩數(shù)相乘,符號(hào)為“+”,先確定積的符號(hào),再計(jì)算絕對(duì)值的積;
(4)根據(jù)有理數(shù)乘法的運(yùn)算方法,異號(hào)兩數(shù)相乘,符號(hào)為“-”,先確定積的符號(hào),再計(jì)算絕對(duì)值的積;
(5)依據(jù)法則是:異號(hào)兩數(shù)相除,符號(hào)為“-”,并把絕對(duì)值相除;
(6)先進(jìn)行冪的運(yùn)算,然后再進(jìn)行加減的運(yùn)算.
解答:解:(1)(-45)+(-23)=-(45+23)=-68;
(2)(-9)+7=-2;
(3)(-4)×(-9)=36;
(4)(-
2)×
=-
×
=-1;
(5)(-63)÷7=-9;
(6)-5
3+2=-125+2=-123.
點(diǎn)評(píng):本題考查了有理數(shù)加法.在進(jìn)行有理數(shù)加法運(yùn)算時(shí),首先判斷兩個(gè)加數(shù)的符號(hào):是同號(hào)還是異號(hào),是否有0.從而確定用那一條法則.在應(yīng)用過(guò)程中,要牢記“先符號(hào),后計(jì)算”.