Question

Reviewing and need refreshing.

Answer 1

\[(4\sqrt{5} - 3\sqrt{2}) (2\sqrt{5}+2\sqrt{2})\]

Answer 2

@jim_thompson5910

Answer 3

to expand out (a+b)(c+d), we use this rule

(a+b)(c+d) = a(c+d) + b(c+d)

then distribute to get

a(c+d) + b(c+d) = ac + ad + bc + bd

Answer 4

so,

(a+b)(c+d) = ac + ad + bc + bd

Answer 5

you may have seen this as the FOIL rule

Answer 6

would it be \[8\sqrt{5}-6\sqrt{2}\]?

Answer 7

let me check real quick, one sec

Answer 8

no that's incorrect

Answer 9

:(

Answer 10

it's not as simple as multiplying the first terms

and multiplying the last terms

then adding them up

Answer 11

have you heard of the FOIL rule?

Answer 12

im sure i have but i dont remember.

Answer 13

FOIL = First, Outer, Inner, Last

Answer 14

it's a mnemonic to help you expand out things that are of the form (a+b)(c+d)

Answer 15

I understand, I'll take it out.

Answer 16

so what you do is multiply

F: First terms --> \(4\sqrt{5} * 2\sqrt{5} = 8\sqrt{5*5} = 8*5 = 40\)

O: Outer terms --> \(4\sqrt{5} * 2\sqrt{2} = 8\sqrt{5*2} = 8*\sqrt{10}\)

I: Inner terms --> \(- 3\sqrt{2} *2\sqrt{5} = -6\sqrt{2*5} = -6*\sqrt{10}\)

I: Last terms --> \(- 3\sqrt{2} *2\sqrt{2} = -6\sqrt{2*2} = -6*2 = -12\)

Answer 17

then you add all those results up to get

\(\large 40 + 8\sqrt{10}-6\sqrt{10} - 12 = 28 + 2\sqrt{10}\)

Answer 18

so that means

\[\large (4\sqrt{5} - 3\sqrt{2}) (2\sqrt{5}+2\sqrt{2}) = 28 + 2\sqrt{10}\]

Answer 19

in the beginnning why do you time 8 and 5?

Answer 20

nevermind. lo9l

Answer 21

oh you see why?

Answer 22

yeah. the square root of 25 is 5

Answer 23

yep

Answer 24

nice @jim_thompson5910

Answer 25

thanks