Question

If
$15x + 17y = 21$
and
$17x + 15y = 11$
then find value of
$x + y$


​

Answer 1

Answer:

15x+17y=21    .....(1)

17x+15y=11   .....(2)

17×eqn(1)−15× eqn(2) gives

255x+289y−255x−225y=357−165

⇒64y=192

⇒y=64192=3

Substitute the value of y=3 in (1) we get

15x+17×3=21

⇒15x=21−51=−30

∴x=15−30=−2

Hence x=−2,y=3

And x+y=−2+3=1