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Course: Digital SAT Math > Unit 8
Lesson 12: Exponential graphs: mediumExponential graphs — Basic example
Watch Sal work through an easier exponential graphs problem.
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- dec 2 ppl? sweaty palms rn. scared ngl. after doing lessons (didn't finish math section yet) I got 1080 in practice 1. I really wanna get at least 1400+(19 votes)
- good luck for the exam ya all(1 vote)
- I aint doin allat just plug it into desmos and see if values match(18 votes)
- Pls I am from Nigeria
Is the June 3 SAT posponed(5 votes)- how did it go(5 votes)
- but i think this theme should be removed as SAT calculator is able to solve this kindda questions(6 votes)
- is anyone writing in november 4th??(4 votes)
- Anyone for May 4th exam?(3 votes)
- I am here! Break a leg y'all(3 votes)
- Can't we just use demsos to graph?(1 vote)
- Yes, Desmos is integrated within the DSAT software(4 votes)
- i didnt get this someone help lol(1 vote)
- i didn't watched the vid, but here's my soln (don't worry it's crct, i checked at the end of the video)
he probably, did it by direct substitution.
So, let's find the y-intercept (i.e., the point where the graph intersects the y-axis). We can find that by putting x=0, so then let's do it.
Here, we can clearly see, that y-intecept is 8.
so we can safely eliminate, all the f(0)≠8
opt a:
f(0) = 7((5/7)^0) + 1 = 7(1)+1 = 8
doing this for the rest of the options we find that , the y-intercept is 8 for all of them.
not let's look further, let's find the y-value when x=1, which on careful observation of the graph tells us that it is 6.
over here lets put,
x = 1 for all option.
let's take opt b.
f(1) = 8((1/8)^1) = 8(1/8) = 1
well that's wrong according to the graph.
let's check opt c
f(1) = 8((3/4)^1) = 8(3/4) = 2*3 = 6
Yay! that's actually correct, so the correct option is c. This might seem a little disconneted (or even weird) method to solve a question, but let's take a trivial example to compare what I did here.
Q. what is 'x' in 2x + 5 = 15?
a) 1, b)7 c)5, d)6
this must be very trivial for you, you can easily solve it in mind and say the ans to be opt c.
But, let's see this thru the mind of a 4th grade who just learnt to solve it, its gonna be kinda hard for him, so cooks up a trick, instead of solving he just puts the options in place of x one by one until its crct like this:
let's take x to be 1, then we get 2(1) + 5 = 7, but we aren't supposed to get 7, lets do opt c, 2(5) + 5 = 10 +5 = 15, yay , that's exactly same as 15, so the crct answer must be option c. And guess what's he's crct.
Thus, we can apply this little logic in senior grade maths to but a little, disclamor, it doesn't always work.
Here's an example of what might not work as well, most likely in the case when all the option on substuting give a similar answer, but there's some messing up in the domain or range, some neat little tricks, that Question Paper makers do.(3 votes)
- the first A should be out as the intial value is not 7, but 8(2 votes)
- anyone got tips for the digital SAT Math section specfically? because i keep getting 650 or 620 even if my goal is 700+(2 votes)