Word Problems

[Diesel]

I'm having a problem in this please i would really appreciate if someone can solve this for me with the formula and everything

 

1- Find the whole number such that four times the number subtracted from three times the square of the number makes 15.

[matt grime]

Let n be an integer such that 3n^2 - 4n=15, find n.

 

Can be done in two ways. one you can use the quadratic formula, but better, factor the left and right and conclude something using uniqueness of prime factorization

[ed84c]

1.66666666 or -3

(using quad form)

[ed84c]

just work through the formula on paper, and you should get that (well I did any way :-S)

[Callipygous]

I'm having a problem in this please i would really appreciate if someone can solve this for me with the formula and everything

 

1- Find the whole number such that four times the number subtracted from three times the square of the number makes 15.

 

3n2-4n=15

3n2-4n-15=0

 

n=(4(+/-)sqrt(16-4(3)(-15)))/6

 

n=(4(+/-)sqrt(16+180))/6

 

n=(4(+/-)14)/6

 

 

 

n=(2+7)/3 n=3

or

n=(2-7)/3 n=-5/3

[matt grime]

In all honesty it is far better to do it with integer factorizations:

 

n(3n-4) = 3*5

 

though in this case you need to consider -3*-5 as an option too.

 

I say this because this techique allows you to solve equations like: find all primes, p such that p+9=n^2 where n is an integer, and we do not even need to consider anything as high faluting as a formula.