can you please explain to me what the letters suppose to mean on this algebra problems that are in the foil method
i still dont understand what the x means or what each letter supoose to mean
Letters are the labels or names for variables, and a variable is something that can change, like the speed limit on roads and highways. Here is an example:
In many states, if you drive 15 mph over the speed limit you are ticketed for reckless driving. So if x represents the speed limit, and the police clock you driving at x + 15 they can give you a ticket for reckless driving. If the speed limit = 55, then x + 15 = 70. If the speed limit is 30, then x+ 15 = 45. We use an equation with variable x to mathematically express the reckless driving law, x + 15 = reckless driving. No matter what the speed limit might be, you can put it in for x and find the speed for a reckless driving ticket.
FOIL is a "recipe" to multiply 2 expressions with variables to get their product.
If we are trying to multiply (x + 7) by (2x - 4) we notice the each of the expressions has 2 terms.
In (x + 7), the x is the First term and the 7 is the Last term.
In (2x - 4), the 2x is the First term and the -4 is the Last term.
Write the letters for FOIL vertically and look at your problem (x + 7)(2x - 4)
F: Mulitply the first terms x times 2x = 2x2 (remember x2 just means x times x)
O: Multiply the outside terms x times -4 = -4x
I: Multiply the inside terms 7 times 2x = 14x
L: Multiply the last terms 7 times -4 = -28
Then add every answer together and combine the like terms: 2x2 + (-4x) + 14x + (-28)
The only terms that can add together are -4x and 14x. They both have x (notice x2 is different) so add -4 and 14 to get 10, so -4x + 14x = 10x
Nothing else combines, so just write it down: 2x2 + 10x + (-28)
When you add a negative, that is the same as subtracting, so this becomes 2x2 + 10x - 28