@florisalreadytaken how

Question

mhanifa · Answer

From the expression we see the first term is -3 and common ratio is 4

mhanifa · Answer

You can use the formula for the sum of the first n terms of GP

mhanifa · Answer

Do you know the formula?

snowflake0531 · Answer

uh $$\frac{a_{1}(r^n-1)}{r-1}$$

mhanifa · Answer

Excellent, you can substitute a1, r and n

Florisalreadytaken · Answer

formulas are just an evaluated conclusion of the problem -- i would suggest you do it the long way around so you understand it better

also, please do not reply this recently on posts -- its a spam nearly

mhanifa · Answer

Are you going to continue or start over?

snowflake0531 · Answer

a1 is 1, r is 4 and n is 5?

Florisalreadytaken · Answer

well this is what we have  $ \sum_{n=1}^{5} -3(4)^{n-1}  ​$

basically, there are 5 different 'parenthesis", where n is $ x+1 $  fpr each one of them

this thing is logic aligned -- from your recent post we saw that the domain is always positive -- as it mentioned, it starts from 1 -- thus we can write:
$$ ( -3(4)^{1-1})-( -3(4)^{2-1} )- ( -3(4)^{3-1}) - ( -3(4)^{4-1}) - ( -3(4)^{5-1})$$
you get it do you not?

snowflake0531 · Answer

yes e.e

snowflake0531 · Answer

$$-3 - (-12) - (-48) - (-192) - (-768) = 1017$$

mhanifa · Answer

@florisalreadytaken wrote:

well this is what we have $ \sum_{n=1}^{5} -3(4)^{n-1} $ basically, there are 5 different 'parenthesis", where n is $ x+1 $ fpr each one of them this thing is logic aligned -- from your recent post we saw that the domain is always positive -- as it mentioned, it starts from 1 -- thus we can write: $$ ( -3(4)^{1-1})-( -3(4)^{2-1} )- ( -3(4)^{3-1}) - ( -3(4)^{4-1}) - ( -3(4)^{5-1})$$ you get it do you not?

I think it is incorrect, please review

snowflake0531 · Answer

?_? why add the 6

mhanifa · Answer

The mistake is you should add up all 5 parenthesis, so + instead of - in between them

mhanifa · Answer

@snowflake0531 wrote:

uh $$\frac{a_{1}(r^n-1)}{r-1}$$

Using this formula is shortest and easiest way

snowflake0531 · Answer

@mhanifa wrote:

@snowflake0531 wrote:

uh $$\frac{a_{1}(r^n-1)}{r-1}$$

Using this formula is shortest and easiest way

a1 is 1, r is 4 and n is 5??

Florisalreadytaken · Answer

formulas are boring -- they teach you nothing!

mhanifa · Answer

@snowflake0531 wrote:

@mhanifa wrote:

@snowflake0531 wrote:

uh $$\frac{a_{1}(r^n-1)}{r-1}$$

Using this formula is shortest and easiest way

a1 is 1, r is 4 and n is 5??

Yes

snowflake0531 · Answer

@florisalreadytaken wrote:

formulas are boring -- they teach you nothing!

damn

snowflake0531 · Answer

$$\frac{4^5-1}{4-1} = \frac{1023}{3}$$

mhanifa · Answer

Sorry, a1 is -3

snowflake0531 · Answer

oh

snowflake0531 · Answer

$$\frac{-3(1023)}{3} = -1023$$

mhanifa · Answer

Correct

snowflake0531 · Answer

thank you o-o

mhanifa · Answer

You are welcome!