Math homework help! FOIL?

Question

My teacher gave us some problems that we have to put into foil form ex. (x+2) (x+3)

8x^2-50

Explanations would be appreciated.

Answer 1

FOIL stands for First, Outside, Inside, Last.  It isn't a form, it's a method for multiplying two binomial expressions...

(x + 2)(x+3)

To multiply by the FOIL method

x*x + 2*x + x*3 + 2*3

x^2 + 5x + 6.

----------------------------

To factor the expression

8x^2 - 50, I start with

(2x +  ?)(4x + ?)

Then try to find two numbers (a and b) such that...

ab = -50

and

2a + 4b = 0

The numbers in question are...

-5 and 10 (or 5 and -10)

So your factors are...

(2x - 5)(4x + 10)

Checking using the FOIL method...

2x*4x -20x + 20x - 50

8x^2 - 50   CHECK

Answer 2

This is acutally a difference of squares.

8x^2-50 take out GCF

2(4x^2-25) difference of squares

2(2x^2-5)(2x^2+5) there you go

P.S. It's the same as the one above, just factored more.

Answer 3

What I usually do is just plug in possible numbers and then test them to see which ones work.

(4x-10)(2x+5) works.

Answer 4

FOIL stands for First Outside Inside Last

Meaning that you multiple the terms in that order and add them.

FOIL form would look like

first times first= x*x=x^2

outside times outside= x*3=3x

inside times inside= 2*x=2x

and last times last= 2*3=6

add all of those together and you get x^2+3x+2x+6

For the second equation you have to work it backwards. First times first has to equal 8x^2 inside and outside have to cancel each other out (one +, one -) and the last terms would have to equal -50. Start plugging in factors of 8 and 50 in to see if they work for example you could try

(8x+50)(x-1) but that = 8x^2-50x+x-50= 8x^2-49x-50 so you'll have to try different factors

Answer 5

F - First Terms

O -  Outer Terms

I - Inner Terms

L - Last Terms

First, multiply the first terms,

(x)(x)

=x^2

Then, multiply the outer terms,

(x)(3)

=3x

Then, multiply the inner terms,

(2)(x)

=2x

Finally, multiply the last terms

(2)(3)

=6

Add all,

x^2 + 3x + 2x + 6

x^2 + 5x + 6

That's the answer...:-)