Question

Find the students error in solving the following inequality 2<-3x-4<5

6<-3x<5
-2>x>-5/3

Answer 1

The student did not add 4 to all sides of the inequality

Explanation:

2<-3x - 4<5

Add 4 to all sides

4 + 2< -3x - 4 + 4 < 5 + 4

6< -3x < 9

Divide all sides by the coefficient of x; -3

-2< x < -3

Remember, when dividing an inequality with a negative number, you must flip the sign

So, this becomes;

-2 > x > -3