✔ 最佳答案
正負數的乘除:
最緊要是記住一條公式,同號得正,異號得負,即正正得正,正負得負,負正得負,負負得正,這是用於兩數相乘或相除的,如果多於兩個數,就要連用公式。
1. (+6)x(-4)
解:(+6)x(-4)
=-(6x4)--------(先確定符號:正負得負)
=-24
2. (+13)(-9)
解:(+13)(-9)
=-(13x9)------(先確定符號:正負得負)
=-117
3. (-18)÷(+6)
解:(-18)÷(+6)
=-(18÷6)-------(先確定符號:負正得負)
=-3
4. (-35)÷(+5)x(-7)
解:(-35)÷(+5)x(-7)
=+(35÷5x7)------(先確定符號:負正得負,負負得正)
=49
5. (-27)÷(-9)-(+16)x(-12)
解:(-27)÷(-9)-(+16)x(-12)
=+(27÷9)-[-(16x12)]---(先確定符號:負負得正;正負得負)
=3+192-----(去括號時留意,括號外是負,括號裏又是負,=195 所以拆開時就變成正)
6. [(+8)-(+12)]x(+6)
解:[(+8)-(+12)]x(+6)
=[8-12]x6
=(-4)x6
=-24-------(確定符號:負正得負)