Question

if x^2-y^2=100 and x-y=20,what is the value of x+y?

Answer 1

\[x ^{2}-y ^{2}=100\]
\[x-y=20\]
\[x+y=?\]

Answer 2

(x+y)(x-y)=x^2-y^2
do you get this part?

Answer 3

@ineedhelpnow08

Answer 4

no....

Answer 5

well if you have an expression in the form of a^2-b^2, then you can factorise it as (a+b)(a-b)

Answer 6

(a+b)(a-b)
a^2+ab-ab-b^2
a^2-b^2

Answer 7

do you get it now?

Answer 8

5

Answer 9

oh..

Answer 10

so now we can replace x^2-y^2 with (x+y)(x-y) to get
(x+y)(x-y)=100

Answer 11

so like its (20)(x+y)=100?

Answer 12

since we know (x-y) = 20, we can write
(x+y)(20)=100
(x+y)=100/20
x+y=5

Answer 13

do you get it now?

Answer 14

thanks!!

Answer 15

haha... good luck with these type of question..

Answer 16

lol S.A.T are hard

Answer 17

haha.. you just gotta work harder...