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Mathematics 14 Online
OpenStudy (anonymous):

Need help for college algebra, desperate, find values for x so that the perimeter of the figure is less than 140 meters. Length of rectangle x+4, width x

OpenStudy (danjs):

2(x+4) +2(x) < 140

OpenStudy (danjs):

the perimeter of a rectangle is 2 sides and 2 widths

OpenStudy (danjs):

2x + 8 + 2x < 140

OpenStudy (danjs):

4x < 132

OpenStudy (danjs):

x < 33

OpenStudy (anonymous):

ok that makes a lot of sense now thank you. @DanJS do you happen to know interval notation too?

OpenStudy (danjs):

u understand all that?

OpenStudy (danjs):

sure ask away

OpenStudy (anonymous):

wait about the last question would it be less than or equal to or just less that, if so why?

OpenStudy (anonymous):

than*

OpenStudy (danjs):

it says in the question that the perimeter is less than

OpenStudy (danjs):

P < 140

OpenStudy (danjs):

ans P = 2(Length) +2(Width) for a rectangle

OpenStudy (anonymous):

ok, sorry that was a dumb question. x<3, write in interval notation, I thought it would be (-infinity,) but I'm not sure.

OpenStudy (anonymous):

(-infinity,3)*

OpenStudy (danjs):

right, if it is just "less than" you use a parenthesis if it is also equal to, you would use a bra - ket

OpenStudy (danjs):

the only restriction is that x is less than 3

OpenStudy (danjs):

(-infinity , 3)

OpenStudy (anonymous):

ok

OpenStudy (danjs):

How about x is greater than 3 but less than or equal to 63

OpenStudy (anonymous):

(3,63] ?

OpenStudy (danjs):

correct, you got it

OpenStudy (anonymous):

Can I ask one more question? I promise its the last, I'm just studying for an exam for monday.

OpenStudy (danjs):

no prob

OpenStudy (anonymous):

Solve the inequality symbolically. The solution set is {t| }

OpenStudy (danjs):

\[\frac{ 5 }{ 4 }(6t-5) \le \frac{ 1 }{ 2 }(16t-7) + 3\]

OpenStudy (danjs):

I would multiply everything by 4 to begin with

OpenStudy (danjs):

\[5(6t-5) \le 2(16t-7) + 12\]

OpenStudy (danjs):

see that?

OpenStudy (anonymous):

yes, so 30t-25≤32t-2

OpenStudy (danjs):

yes

OpenStudy (anonymous):

-2t<=23

OpenStudy (danjs):

yes

OpenStudy (anonymous):

t>=-11.5

OpenStudy (danjs):

yes! you switched the sign because you divided by a negative number.

OpenStudy (danjs):

so the interval is then?

OpenStudy (anonymous):

so is the solution set just 11.5?

OpenStudy (danjs):

oh

OpenStudy (danjs):

{t such that t >=11.5} the "such that" is the vertical line

OpenStudy (anonymous):

or is the solution set also in interval notation?

OpenStudy (danjs):

no they wanted it in that notation, which reads "All t, such that t is greater than or equal to 11.5"

OpenStudy (anonymous):

So when I get a problem on the test like this one would I just put -11.5 in the gap?

OpenStudy (danjs):

the vertical line is "such that" the gap would be your inequality

OpenStudy (anonymous):

so t >=-11.5

OpenStudy (danjs):

yeah, that is what that notation does, it states the variable "all t" vertical line "such that" then restrictions if any

OpenStudy (danjs):

if no restrictions, then

OpenStudy (anonymous):

Ok, so just to be clear on interval notation, if I do -5<x<=6, it would be like (-5,6]

OpenStudy (danjs):

\[t \epsilon \mathbb{R} \]

OpenStudy (danjs):

t is an element of the real numbers, if there are no restrictions,

OpenStudy (anonymous):

ok, that makes sense. Ok, so just to be clear on interval notation, if I do -5<x<=6, it would be like (-5,6]

OpenStudy (danjs):

yeah you are right

OpenStudy (anonymous):

ok thank you, i really appreciate your help.

OpenStudy (danjs):

np, feel free to ask anytime, you are one of very few that actually want to understand and not just given answers. :)

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