Question

find the value of (x+y). if 15x+17y=21
and 17x+ 15y =11​

Answer 1

Answer:

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Step-by-step explanation:

The given equations are,

15x+17y=21                      ------- ( 1 )

17x+15y=11                       ------- ( 2 )

Multiplying equation ( 1 ) by 17 we get,

⇒   225x+289y=357         ----- ( 3 )

Multiplying equation ( 2 ) by 15 we get,

⇒  225x+225y=165         ----- ( 4 )

Now, subtracting equation ( 4 ) by equation ( 3 ) we get,

⇒  64y=192

∴  y=3

Substituting y=3 in equation ( 1 )

15x+17(3)=21

15x+51=21

15x=−30

∴  x=−2

⇒  (x−y)=−2−3=5

Answer 2

15x+17y=21 ....(1)

17x+15y=11 ...(2)

17×eqn(1)−15× eqn(2) gives

255x+289y−255x−225y=357−165

⇒64y=192

⇒y= 182/64

y =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 ans.