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Mathematics 17 Online
OpenStudy (amtran_bus):

Inequality

OpenStudy (amtran_bus):

Why is it greater than or equal to 0 and not less than and equal to?

OpenStudy (amtran_bus):

I was saying \[x(x-6)\le0\] \[x-6\le0\]

OpenStudy (amtran_bus):

Solvin to get x le 6

OpenStudy (amtran_bus):

and x le 0 (le = less than, equal to)

ganeshie8 (ganeshie8):

tell me this, ab \(\le\) 0

ganeshie8 (ganeshie8):

does tha tmean, \(a \le 0\) , and b \(\le\) 0 ?

OpenStudy (amtran_bus):

It means the two multiplied together is less than or equal to zero?

ganeshie8 (ganeshie8):

yes, so ?

ganeshie8 (ganeshie8):

when is that possible ? the product ab to be le 0

ganeshie8 (ganeshie8):

is it possible when both a & b are negative ?

OpenStudy (amtran_bus):

One would have to be negative and the other positive. Otherwise it would be greater than?

ganeshie8 (ganeshie8):

yup ! a & b both positive also wont work

OpenStudy (amtran_bus):

How do you know which one which on the original ??

ganeshie8 (ganeshie8):

lets go back to ur original problem and see :)

ganeshie8 (ganeshie8):

\(x(x-6)\le 0 \)

ganeshie8 (ganeshie8):

we knw for sure that x and (x-6) can NOT have same signs

OpenStudy (amtran_bus):

Right.

ganeshie8 (ganeshie8):

right ? that much is obvious eh

ganeshie8 (ganeshie8):

good :) we're left wid two cases 1) x positive, (x-6) negative 2) x negative, (x-6) positive

OpenStudy (amtran_bus):

Got that

ganeshie8 (ganeshie8):

check each of them if they satisfy the inequality

ganeshie8 (ganeshie8):

1) x positive, (x-6) negative \(x\ge 0\), \(x-6 \le 0\) \(x\ge 0\), \(x \le 6\) this is one solution set, lets see if other case gives something

ganeshie8 (ganeshie8):

2) x negative, (x-6) positive \(x \le 0 , x-6 \ge 0\) \(x \le 0 , x \ge 6\) NOT POSSIBLE for the x to be less than 0, and greater than 6, at the same time !

ganeshie8 (ganeshie8):

so, oly solutions are from case 1 above

OpenStudy (amtran_bus):

You are awesome @ganeshie8 Can you help me put this in interval notation?

OpenStudy (amtran_bus):

Since

ganeshie8 (ganeshie8):

from case 1, we have \(x \ge 0 , x \le 6\) \( 0 \le x \le 6\)

ganeshie8 (ganeshie8):

you wanto put it in interval notation ?

OpenStudy (amtran_bus):

Right. I got this below:

ganeshie8 (ganeshie8):

below interval notation :- [0, 6]

OpenStudy (amtran_bus):

The brackets meaning equal to.

ganeshie8 (ganeshie8):

yup !!

OpenStudy (amtran_bus):

GOD BLESS YOU!

ganeshie8 (ganeshie8):

lol, one small trick when doing these

ganeshie8 (ganeshie8):

u familiar wid parabolas ? quadratic equations ?

ganeshie8 (ganeshie8):

\(x(x-6)\le0 \) see that, left side is a quadratic, wid x intercepts at 0 and 6

OpenStudy (amtran_bus):

absolutely.

ganeshie8 (ganeshie8):

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