i understand that you have to multiply and cancel out the square roots when multiplied together but what about when you multiply 8 by the square root?

open parentheses 8 plus square root of 10 close parentheses open parentheses 8 minus square root of 10 also written (8+ sqrt10)(8-sqrt10)

Question

i understand that you have to multiply and cancel out the square roots when multiplied together but what about when you multiply 8 by the square root?


open parentheses 8 plus square root of 10 close parentheses open parentheses 8 minus square root of 10  also written (8+ sqrt10)(8-sqrt10)

amistre64 · Answer

you might want to think of this in more general terms:

(a+b) (a-b)

what do we get when we expand this out?

anonymous · Answer

a^2-ab+ba-b^2

amistre64 · Answer

good:  now notice that the middle terms cancel and we are left with a^2 - b^2

amistre64 · Answer

therefore:   (8+ sqrt10) (8-sqrt10) = 8^2 - (sqrt(10))^2

anonymous · Answer

wouldnt that just be 64- sqrt100

amistre64 · Answer

yep

anonymous · Answer

64 minus 16 square root of 10

 64 minus square root of 10

 74

 54
the thing is these are the answer choices

amistre64 · Answer

then you might want to keep simplifiy it ....

amistre64 · Answer

you posted:  "i understand that you have to multiply and cancel out the square roots when multiplied together"

yet you didnt do that did you ...

anonymous · Answer

oh

anonymous · Answer

oh is the answer 54?