Mathematics for IGCSE & O level - Inequalities (Section 1 - No. 44)
Which expression requires reversing the inequality sign when solving?
Adding a positive number to both sides.
Subtracting a positive number from both sides.
Multiplying by a positive number on both sides.
Multiplying by a negative number on both sides.
解释
When multiplying or dividing by a negative number, the sign reverses.