Mathematics for IGCSE & O level - Inequalities (Section 1 - No. 14)
When multiplying or dividing an inequality by a negative number, what must you do?
Do nothing; the inequality stays the same.
Reverse the inequality sign.
Add a negative sign to the result.
The inequality becomes undefined
Giải thích
You must reverse the inequality sign. (e.g., If 4 < 7, then multiplying both sides by -2 results in -8 > -14)