Question

Suppose that a + b = 3 and a^2 + b^2 = 7. Then a^4 + b^4 is equal to

Answer 1

\[(a^2+b^2)^2=7^2\]

Answer 2

\[a^4+2a^2b^2+b^4=49\]

Answer 3

is (a^2 + b^2)^2 = a^4 + b^4 ?

Answer 4

\[a^4+b^4+2a^2b^2=49 => a^4+b^4=49-2a^2b^2\]

Answer 5

no

Answer 6

it is what i said

Answer 7

\[(a^2+b^2)^2=a^4+2a^2b^2+b^4\]

Answer 8

i see ..

Answer 9

\[(a+b)^2=3^2 => a^2+2ab+b^2=9\]

Answer 10

\[a^2+b^2=9-2ab\]
But what does \[a^2+b^2=?\]

Answer 11

7 right?

Answer 12

so 9-2ab=7

Answer 13

solve for ab

Answer 14

\[-2ab=-2 => ab=1\]

Answer 15

so if ab=1 then \[(ab)^2=?\]

Answer 16

Remember we have this
\[a^4+b^4=49-2a^2b^2\]

Answer 17

we know \[(ab)^2=a^2b^2\]

Answer 18

so if \[ab=1 \text{ what is } (ab)^2=?\]
@cuty_shai2000 ?

Answer 19

a^4 + b^4 = 47?

Answer 20

49-2 = 47? hmm

Answer 21

yep yep :)

Answer 22

now i know, thanks so much.

Answer 23

np