Question

if x-y=5,xy=6 then what is x+y?

Answer 1

Answer:

given:

x-y=5 => x=5+y.......1

and xy=6........2

subs 1 in 2,

xy= 6

(5+y)y=6

5y+y²=6

y²+5y-6=0

y²-6y+y-6=0

y(y-6)+1(y-6)=0

(y+1)(y-6)=0

=> y= 6, -1

subs y in 2

if y=6 then, xy=6

x(6)=6

x=1

=> x=1, y=6......3

if y=-1 then, xy=6

x(-1)=6

x= -6

=> x=-6, y=-1

from 3, x+y= 6+1= 7

from 4, x+y= -6+(-1)= -7

hope it helps u......^_^