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Mathematics 20 Online
lolokrat:

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iGreen:

Any ideas?

iGreen:

Why don't we start by simplifying the first two answers and converting the last two into expressions?

iGreen:

5x > 35 or 5x < -35 Can you solve these for 'x'?

iGreen:

Yes, you get those, but you need to keep it in the same form. x > 7 x < -7

iGreen:

Is -6 a solution to this?

iGreen:

Yep, so move on to the next one.

iGreen:

-8 < x - 5 < 3 Can you simplify this?

iGreen:

Yep! You want to isolate 'x' so you have to add 5 to all sides.

iGreen:

Now is -6 a solution to this one?

iGreen:

That's correct, so move on to the next one, can you change that into expression form like the first two options?

iGreen:

"Two less than a number tripled" Can you change that

iGreen:

Yep, now do the last part of it. "at least -5 and at most 1"

iGreen:

Do 'at least' first...what inequality symbol is that?

iGreen:

Not exactly, try answering my question above.

iGreen:

No, if you say "I have at least $5", what does that mean?

iGreen:

Exactly, so 'at least' means \(\ge\)

lolokrat:

-5≥1

iGreen:

So we know that \(\sf 3x-2\ge -5\).

iGreen:

No, these are in relation to '3x - 2'. Now what does 'at most' mean?

iGreen:

Yes...if you say "I have at most $5", that means I could have $5 or less, which is \(\le\).

iGreen:

So we also know that \(\sf 3x-2\le 1\)

iGreen:

Is -6 a solution to \(\sf 3x-2\le 1\) or \(\sf 3x-2\ge -5\) ?

iGreen:

Remember, it has to be true for both, just plug in '-6' for 'x' in each one.

iGreen:

Yep, so on to the last one.

iGreen:

"The sum of 3 times a number and 5" What does that translate to?

iGreen:

Yep, you got it. What about "is between -16 and 11"?

iGreen:

Well, it says 'is between', so we know it can't be equal to either -16 or 11. To be between -16 and 11, what must be true about the relationship to 11? Does it have to be less than or greater than 11?

iGreen:

Yep, because -16 is less than 11. What about -16? Does it have to be less than or greater than -16?

iGreen:

You got it. Because 11 is greater than -16. So we know that 3x + 5 < 11 and 3x + 5 > -16. We can write this as: -16 < 3x + 5 < 11 Now plug in -6 for 'x' and see if it works.

iGreen:

Yes, when you plug in -6 you get: -16 < -13 < 11 -13 is certainly greater than -16 and less than 11. So D is our answer.

iGreen:

\(\huge\checkmark\)

iGreen:

No problem.

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