Question

Find the error.
−5(x + 4) + 21 ≥ −3 + 4(x − 8)
−5x − 20 + 21 ≥ −3 + 4x − 32
−5x + 1 ≥ 4x − 35
−9x ≥ −36
x ≥ 1

Answer 1

When dividing by −9, he did not change the ≥ to ≤.

He subtracted 4x from both sides when he should have added 5x.

He subtracted 1 from both sides when he should have added 36.

He did not make a mistake

Answer 2

\(\bf -5(x + 4) + 21 \ge -3 + 4(x - 8)\\\\ \quad \\
-5x - 20 + 21 \ge -3 + 4x - 32\\\\ \quad \\
-5x + 1 \ge 4x - 35\\\\ \quad \\
\color{red}{-9x \ge -36\\\\ \quad \\
x \ge 1}\)

Answer 3

notice anything there?

Answer 4

Same thing as the equation above. right?

Answer 5

well... what do you mean?

Answer 6

It's the same as what I put.

Answer 7

ohh yes

Answer 8

So I didn't notice anything different..

Answer 9

well, true... I didn't say check for typos, I meant, do you notice anything wrong in the simplification?

Answer 10

the last step will be x<or equal to 4

Answer 11

bcoz when u cancel negative sign on both the sides...the sign will also chnge...it will become less than..and it will be 4 as 36/9 is 4 not 1

Answer 12

so, the error is not switching the signs around ?

Answer 13

well, check again, what do you think is the error?

Answer 14

or....try to simplify it yourself, see what you get

Answer 15

jst check the last two steps...wat is 36 divided by 9?

Answer 16

1 or 4?wt d o u think?

Answer 17

4

Answer 18

yes right..and as i said...if negative sign is present on both the sides..it gets cancelled and the sign chnages.dis is a rule...if u cancel negative on both side sign of equality chnges.u have to remeber dis.