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/sci/ - Science & Math

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4965060 No.4965060 [Reply] [Original]

Somebody help me, i dont what to do and i have a test tomorrow. How do i solve this: (2√5+3√3)^2

>> No.4965120

19

>> No.4965123
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4965123

FOIL.

>> No.4965128

>>4965123


you best be trollin

otherwise gtfo /sci/

>> No.4965144
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4965144

>>4965128
=(2√5)^2 + 2(6√15) + (2√3)^2
=20 + 8√(15) + 12
=22 + 8√(15)

FOIL. Not that hard. In fact, designed to be easy.

>> No.4965162

>>4965144
I had a teacher who hated the term FOIL. He wanted us to understand that it was just distributed multiplication, not memorize the word and do it by rote.

Man, he was a jerk.

>> No.4965213

>>4965162

He was RIGHT.

What're you gonna do when you have to multiply trinomials?

>> No.4965216

>>4965162
>try to teach my students to gain an intuitive understanding of math instead of relying on pointless "shortcuts"
>get called a jerk
>other math teacher loved by every student for teaching methods that will come back to bite her students in the ass in college.
>morality won't allow me to do the same, no matter how much they hate me, because i'll gladly take it if it means their success
such is the life of a caring teacher /sci/.....

>> No.4965220

>>4965216
I never though FOIL made sense. I just did it in the order it was supposed to be done.

>> No.4965226

Yeah, FOIL is a waste of time. It should only be used when people are having chronic trouble grasping basic math, and aren't likely to continue in math. OP.

>> No.4965230

>>4965216
>because he's the hero these students deserve, but not the one they need right now. so we'll hate him, because he can take it.

>> No.4965273

>>4965216
Oh, he was absolutely right about not mindlessly memorizing FOIL. He was a jerk for other reasons, though.

Guy used to brag about how telling people he was a calculus teacher intimidated them because they knew he was super smart. For fuck's sake.

>> No.4965402

>>4965144
You fail so hard
(2√5+3√3)^2
= (2√5)^2 + 2(2√5)(3√3) + (3√3)^2
= 20 + 12√5√3 + 27
= 47 + 12√15

>> No.4965428

What does FOIL stand for?

>> No.4965550

>>4965428
Something among the lines of First outside inside last, aka you start by the first term, multiply it by the first and second etc.

But really, all there is to this (highlighted the used term):
(a + b)^2 = (A + b)*(a + b) = A*(a +b) + b*(a+b) = A*a + A*b + b*(a + b) = a^2 + ab + Ba + Bb = a^2 + ab + ba + b^2

And since multiplication is commutative, ab = ba, then:
a^2 + 2ab + b^2
is the final result.

(I should really learn LaTeX. This is terrible.)