Helppppp with math.?

Question

Hey guys i have a math test 2 morrow and these r some questions on the test and i need to pass lol..

I need to factor

1. 5n-80

2.3x^2+15-45

And I have to find the area of a regular Pentagon with a side of 10.

thank you so much .....please help =D

P.s - this means squared-^2

Answer 1

1. 5n-80
=5(n - 16)

2. 3x^2+15-45
= 3x^2 -30
=3(x^2 -10) .

Answer 2

Factoring means finding "what times what" making 5n-80.

Think of it like this.

If you have a rectangle, and you know the area is 30, and we ask you to find the dimensions, you could say 6 and 5, or 15 and 2, or 10 and 3. That is factoring, or finding the factors of 30.

Now, picture you have a rectangle and the "area" is 5n-80.

Let me give you a hint: one of the dimensions is 5.

Now, what times 5 is 5n-80?

Of course, people are going to give you the answer, but without knowing the why behind it, no amount of help here on Yahoo Answers will aid you in passing your test.

On the second one, you may have a misprint...double check that. I believe you are missing an x there somewhere.

The third one, there is a simple formula...check that out first.

Answer 3

1. 5n - 80
5(n - 16)
factors are 5 and n - 16

2. 3x^2 + 15 - 45
3x^2 - 30
3(x^2 + 10)
factors are 3 and x^2 + 10
x^2 + 10 doesn't factor unless you need imaginary factors.

3. Break the Pentagon into 6 equalateral triangles.
Using trig each triangle must have a height of (5)sqrt(3)
area = (base * height / 2) * 6
area = (10 * (5)sqrt(3)) * 6
area = 60 * (5)sqrt(3)
area is about 519.615

Answer 4

5n-80 = 5(n-16)

if you divide the 5n-80 by 5, that is what you get

3x^2 +15 -45 (i think you meant 15n instead of 15) = 3( x^2+5-15)

sorry, it will take me a while to solve the pentagon problem
will be back soon

Answer 5

if f(x)= 5n-80
then do hit and trial method
so, f(16)=5*16 - 80
= 0
therefore, one of the factors is = (n-16)
you can check it by long devision

for the 1st one = 3(x^2 + 10) so the factor is 3

devide the pentagon into equilateral triangles and find their are
(are of a triangle = 1/2 h*b )

Answer 6

5n + 80

5(n + 16)

- - - - - - -

3x² + 15 - 45

3x² - 30

3(x² - 10)

- - - - - - -s-

Answer 7

pay attention in class..............don't mind me i just need some points