if 9x+8y=17 and 8x+9y=0 then find the value of x+y
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9x+8y=17....1 and 8x+9y=0...2
multiply equation 1with 8 and equation 2 with 9
8(9x+8y=17)
72x+64y=136....3
(8x+9y=0)×9
72x+81y=0....4
from equation 3 and 4
72x+64y-72x-81y=136-0
-17y=136
y=-136/17=-8
from equation 2
8x+9y=0
8x+9×-8=0
8x-72=0
8x=72
x=72/8=9
x+y=9-8=1
therefore, x+y is 1
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