Question

Find the student’s error in solving the following inequality.

31 < –5x + 6
25 < –5x
–5 < x

The student should have added 6 to both sides instead of subtracting it.

The student divided 25/–5 incorrectly.

The student should have switched the direction of the inequality sign to get –5> x for a final answer.

Answer 1

it is the last one. the student should have switched the direction of the inequality.

Explanation:

we know product of 2 negative is positive

in the given condition -5 < x. which means that x is greater than -5 so the values of x will be -4, -3, -2 and so forth.

but if this the case then if we take -3 for example and put it in the top equation we get 31 < -5x-3 + 6 = 31<21 this is wrong.

but if it is -5>x this means the value of x is -6,-7,-8 and so forth. if we apply this now for example if we take -8 or -10 and put it in 31 < -5 X -10 + 6 we get 31<56 which is correct. I hope you get the logic.