RE: Member Photos
September 21, 2017 at 10:18 am
(This post was last modified: September 21, 2017 at 10:20 am by Whateverist.)
(September 20, 2017 at 9:42 pm)Nymphadora Wrote: She threw this at me:
(E+2)(E+2)
I never was good in math. Because of this, I didn't have to learn algebra. I'm 46. She's trying to teach me how to use something that in 46 years of my being on this earth, I've never needed.
She tried teaching me how to foil. The only thing I remotely know about foiling has to do with a hair color technique and you don't need algebra for that!
So...kudos to everyone who is smart enough to understand it. I don't think I ever will.
I like your daughter. Try this: experiment with multiplying 12 by 11 which should come out as 132.
Can we split one of them up as a sum? 11 = 10 + 1
12(10 + 1) So will twelve 10's and twelve 1's give the same result as twelve 11's?
12(10) = 120 and 12(1) = 12 and 120 + 12 = 132 [Yup, good so far.]
What about if we also split the 12 up into the sum of 10 and 2, while still leaving 11 expressed as the sum of 10 and 1?
(10 + 2)(10+ 1) We'll follow the same plan of attack, but use (10 + 2) 10's and (10 + 2) 1's.
(10 + 2)10 and (10 + 2)1 Since order is irrelevant for multiplication we'll write it as
10(10 + 2) and 1(10 + 2) So we need ten 10's, ten 2's, one 10, and one 2 = 100 + 20 + 10 + 2 = 132 [Still good.]
We just 'F.O.I.L.'ed (10 + 2) and (10 + 1). F.O.I.L. actually becomes useful when some of the numbers are variables, you know, the dreaded letters representing an as yet unknown number.
Okay, I'll stop now.
Doh! This is what happens when I don't read all the posts after a post I want to respond to. Poca, you ninja!
(September 21, 2017 at 6:45 am)pocaracas Wrote:(September 21, 2017 at 6:23 am)Nymphadora Wrote: Red mine.
You had me clear up to that point. Then you lost me.
Gotcha... let's try with numbers, then!
3*(9 + 5) = ???
Because we have those parenthesis in there, we are saying that whatever is inside them must be calculated before what comes on the outside - this is part of the language I mentioned.
So that becomes:
3*14 = 42.
But that's the same as splitting the multiplication in two a*(b+c)= a*b + a*c:
3*9 + 3*5 = 27 + 15 = 42
and is substantially different from
3*9 + 5 = 27 + 5 = 33
The parenthesis make a difference in the order of the calculations.
As a general rule, multiplications and division are carried out before sums and subtractions. The parenthesis force us to carry out whatever is inside them first, regardless of the operators on the outside.
You can have enclosed expressions in parenthesis inside parenthesis. When that happens, you should process the innermost one first, and then work all the way to the outermost one.
For example:
3*(9*(4+2)+5) =
= 3 * ( 9*6 + 5) = { or 3 * (9*4 + 9*2 + 5) = 3 * (36 + 18 + 5) }
= 3 * (54 + 5) = {Note how the multiplication got calculated first, inside the parenthesis - general rule applies for each expression}
= 3 * 59 =
= 177