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Mathematics 17 Online
iosangel:

inequality -4(7x-3)<12

Hero:

For this one, here's what to do: Add -4(7x - 3) to both sides. Then subtract 12 from both sides.

iosangel:

like this -4(7x - 3+ -4(7x - 3)<12+ -4(7x - 3)

iosangel:

Im so confused

Hero:

Nope not like that

iosangel:

How will i do it?

Hero:

If you add 4(7x - 3) to both sides, you get 0 < 12 + 4(7x - 3)

Hero:

Now try subtracting 12 from both sides.

iosangel:

Not sure how to do that Like this maybe 0 < 12 + 4(7x - 3)-12?

Hero:

Subtract 12 from BOTH SIDES. You only subtracted it from one side.

iosangel:

12-0<12+4(7x - 3)-12

Hero:

Nope you added 12 to the other side rather than subtract it. You have MINUS 12 on one side and PLUS 12 on the other.

iosangel:

Tbh im confused

iosangel:

where do i subtract the 12

Hero:

Here's what you should have if you subtracted 12 on both sides: 0 -12 < 12 - 12 + 4(7x - 3)

iosangel:

ok

iosangel:

what do i do now?

Hero:

Simplify the expression. What is 0 - 12 and what is 12 - 12

iosangel:

0

Hero:

Write the simplified expression after performing those operations.

iosangel:

0 -12 < 12 - 12 + 4(7x - 3) -12<0+4(7x-3)

Hero:

which simplifies to -12 < 4(7x - 3)

Hero:

Now, the next step is to apply the distributive property

iosangel:

ok -12 < 4(7x - 3) -12<4*28x-12 like this?

Hero:

I think you meant to write -12 < 28x - 12

Hero:

You already multiplied 4 times 7 to get 28 so there's no need to write 4 again.

iosangel:

yes

iosangel:

-12 < 28x - 12 do i solve 28x - 12 now?

Hero:

You solve for x

Hero:

The next step is to now add 12 to both sides.

iosangel:

ok -12+12 < 28x - 12+12 28x>0

iosangel:

28x<0*

Hero:

I don't know what you did, but I did not mention anything about flipping signs

Hero:

The inequality is like an arrow. You have to pay attention to where it is pointing.

Hero:

28x>0 is correct. The other is not.

iosangel:

i didnt mean to flip the sign

iosangel:

Is there more to the problem?

Hero:

The next step is to divide both sides by 28 to isolate x

iosangel:

ok

iosangel:

28x/28<0/28 x<0 this?

Hero:

Why do you keep flipping signs?

Hero:

I only tell you to perform a specific step

iosangel:

idk where the sign goes

Hero:

I never said ever to flip a sign. That's what confuses students. So I was trying to show you how to do this without flipping the sign

iosangel:

oh

Hero:

The answer is not x < 0

iosangel:

x<28?

Hero:

Nope, not that either.

Hero:

Go back to the last known correct step

iosangel:

oh flip the sign?

iosangel:

idk honestly

Hero:

Flipping the sign is not a step in the solution I was showing you

Hero:

You had it mostly right until the very end.

Hero:

You got it wrong after I told you to divide both sides by 28

iosangel:

oh ok

iosangel:

28x/28<0/28 0<28 Like this idk

iosangel:

I didnt flip signs this time

Hero:

The last known correct step was 28x > 0. Then if you divide both sides by 28 you get x > 0

Hero:

Let me show you the full steps though.

Hero:

Original Problem: -4(7x-3)<12 Add 4(7x - 3) to both sides to get: 0 < 12 + 4(7x - 3) Subtract 12 from both sides to get: -12 < 4(7x - 3) Apply the distributive property to get: -12 < 28x - 12 Add 12 to both sides to get 0 < 28x Divide both sides by 28 to get: 0 < x This next step is actually not flipping the sign. It is re-arranging the inequality so that x is on the LHS: x > 0 At no point did I flip a sign. Flipping the sign is an entirely different process.

iosangel:

Ok this is much clearer

Hero:

In fact, you could leave it as 0 < x

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