正无穷大加正无穷大等于多少?负无穷大加正无穷大等于多少?负无穷大加负无穷大等于多少?如果是乘呢?

问题描述:

正无穷大加正无穷大等于多少?负无穷大加正无穷大等于多少?负无穷大加负无穷大等于多少?如果是乘呢?

+∞ + +∞ = +∞
-∞ + +∞ =不确定
-∞ + -∞ = -∞
+∞ × +∞ = +∞
-∞ × +∞ =-∞
-∞ × -∞ = +∞