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Mathematics 11 Online
OpenStudy (itrymath):

gg

OpenStudy (itrymath):

@sooobored

OpenStudy (sooobored):

so what do you not understand?

OpenStudy (itrymath):

whole thing.....

OpenStudy (sooobored):

ok, firstly, f(x) - denotes a function or is the way of saying, "this equation is a function"

OpenStudy (sooobored):

\[f(x) = a(b)^x\] and \[f(x)= P(1+r)^x\] are both different forms of exponential functions

OpenStudy (sooobored):

notice how the 2 equations are similar if you set a = P and b= 1+r

OpenStudy (sooobored):

first first form is the more general exponential function the 2nd form is used mostly when calculating compound interest problems

OpenStudy (sooobored):

any questions thus far?

OpenStudy (itrymath):

uh yeah ... what do i write down into my notebook?

OpenStudy (itrymath):

oh nothing yet okay

OpenStudy (sooobored):

uhhh, whatever you think is important?

OpenStudy (itrymath):

okay so what am i suppose to think of?

OpenStudy (sooobored):

i do not know what you are saying the 2 functions are very basic forms which would be immensely helpful if memorized

OpenStudy (sooobored):

from what you showed, it defines that a is the y-intercept where the y-intercept is the point on the y-axis having the form (0,a)

OpenStudy (itrymath):

No i understand but what is exactly my homework?

OpenStudy (sooobored):

there is no homework from what you showed me

OpenStudy (itrymath):

because imr eading it and cant understand whats its asking me

OpenStudy (itrymath):

Oh are you serious

OpenStudy (sooobored):

its all basic information and definitions

OpenStudy (itrymath):

WAIT !!!! I got it ooops!

OpenStudy (sooobored):

i dont see any question marks hence no questions

OpenStudy (itrymath):

those are the questions

OpenStudy (sooobored):

number 1 is asking you to write down a function for the population of snails since it states that the growth is exponential, the function of population would be an exponential function then explain what the variables you wrote down mean in complete sentences

OpenStudy (itrymath):

okay i see

OpenStudy (sooobored):

if we are to consider population and time into a coordinate system, we would make the x-axis as time (years since its asking for growth over 15 years, you could do months in which case it would be 600 months) and y-axis would be total population of snails, since that is changing over time

OpenStudy (sooobored):

so which of the 2 forms of exponential functions would you use? and what would the variables mean in your snail case?

OpenStudy (itrymath):

f(x)=a(b)^x

OpenStudy (sooobored):

ok, and what is the meaning of a?

OpenStudy (itrymath):

Snails

OpenStudy (sooobored):

not specific enough

OpenStudy (sooobored):

as the basic information stated, a is the y-intercept in our snails case, this means the point (0,a) meaning at time 0 the population of snail is a thus "a" must mean the initial population of snails we started with

OpenStudy (sooobored):

ok, what does b mean?

OpenStudy (itrymath):

OH okay

OpenStudy (itrymath):

B means decreasing of snails

OpenStudy (itrymath):

or wait

OpenStudy (itrymath):

B is rate of growth sorry

OpenStudy (sooobored):

yes, rate of growth, if i said that the population doubles every year, what value would b be?

OpenStudy (itrymath):

rate of growth still?

OpenStudy (sooobored):

what number- value

OpenStudy (sooobored):

b=? if i said teh population is doubling every year

OpenStudy (itrymath):

b= doubled rate of growth .

OpenStudy (sooobored):

no, b=2

OpenStudy (itrymath):

wa

OpenStudy (sooobored):

if the population tripled every year, b=3 quadrupled b=4

OpenStudy (sooobored):

does this make some sense, or do you totally not understand?

OpenStudy (itrymath):

oh okay i see!

OpenStudy (itrymath):

I totally understand

OpenStudy (itrymath):

so i can write tht b=1 and or b= rate of growth

OpenStudy (sooobored):

no b=1 means that population wouldnt change from year to year since you multiply the initial population by this rate "b"

OpenStudy (itrymath):

Oh okay is see why not

OpenStudy (sooobored):

assuming we start with a population of "a" snails after the first year, we would have b*a snails after the 2nd, we would have b*b*a snails 3rd, b*b*b*a

OpenStudy (sooobored):

etc

OpenStudy (itrymath):

yeha i get it

OpenStudy (sooobored):

ok side questions, if i said the population was half every year, then what would the rate be?

OpenStudy (itrymath):

for #2 i would pick f(x)=a(b)^x

OpenStudy (sooobored):

#2 is asking something totally different

OpenStudy (itrymath):

b=100 something?

OpenStudy (sooobored):

still on #1

OpenStudy (sooobored):

population is being halved every year, b=?

OpenStudy (itrymath):

b=100 something

OpenStudy (itrymath):

or no 6

OpenStudy (itrymath):

or -6

OpenStudy (sooobored):

being halved means that population is decreasing 100 ->50-25-12.5 ... so why wouldnt it be b=1/2 ?

OpenStudy (itrymath):

because half a year doesnt mean 1/2

OpenStudy (itrymath):

it means 6

OpenStudy (sooobored):

no no, being halved per year every year, the population is divided by 2

OpenStudy (sooobored):

if we assume every x unit is a year then after year 1, then we would divide the total pop by 2 or multiply by 1/2

OpenStudy (sooobored):

b is the value in which you modify the initial population by

OpenStudy (itrymath):

oh

OpenStudy (sooobored):

if its growing, b is greater than 1 if its decreasing, b is less than 1 but greater than 0

OpenStudy (sooobored):

if b is negative, then that doesnt make any sense in our problem, how can you have a negative amount of snails? and then have a positive amount of snails the next year?

OpenStudy (sooobored):

ok, i think i've explained enough to thoroughly answer #1 any questions?

OpenStudy (itrymath):

i dont think so after that explanation

OpenStudy (itrymath):

not in bad way but good way

OpenStudy (sooobored):

ok your question number 2 is an application of power of a power property read through that and then tell me if you still dont know how to do #2

OpenStudy (itrymath):

so i wrote A= population of snails B= rate of change x= (not sure)

OpenStudy (sooobored):

x is the year after 1 year- you would set x=1 and solve for the total population f(1) after 2 years- you would set x=2 and solve for the total population f(2) 3 years 4 years etc

OpenStudy (itrymath):

OpenStudy (sooobored):

the 15 years doesnt mean much,the function you wrote down gives you the total population after x years if you wanted to solve the population after 15 years, you would set x=15 and find f(15)

OpenStudy (itrymath):

oh so should i write down x= years in rate of growth

OpenStudy (sooobored):

x would the the number of years that pass it has nothing to do with rate of growth

OpenStudy (itrymath):

okay mvoing to number 2

OpenStudy (sooobored):

right, as i said, application of power of power rule read through that, read through taht question try to figure it out, show me steps, and if you still dont understand, say something

OpenStudy (sooobored):

question is asking you to make the power x instead of 2x

OpenStudy (itrymath):

yeah nore sure how.. but my teacher went over this a bit i think

OpenStudy (itrymath):

wouldn't we multiply 1.03*2 and then the outcme would be 2.06^2

OpenStudy (itrymath):

2.06^x

OpenStudy (sooobored):

close but you dont multiply

OpenStudy (itrymath):

divide?

OpenStudy (sooobored):

"power" of "power"

OpenStudy (itrymath):

what does tht mean?

OpenStudy (sooobored):

ok, so the power of power property says if you have a power to a power then instead of taking the power to the power you can multiply them instead so \[n^{x^y} = n^{xy}\]

OpenStudy (itrymath):

uuuh

OpenStudy (itrymath):

not familiar with that

OpenStudy (sooobored):

but it also means that you can group them so commutative property \[xy=yx\] and \[(n^x)^y = n^{xy}= (n^y)^x\]

OpenStudy (sooobored):

what i wrote above is an extension of the power to power property that was not clearly defined in whatever material is given to you

OpenStudy (sooobored):

remember that rule an exponent to an exponent is the equivalent of multiplying the two exponent numbers together

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