Question

if X + Y is equal to 6 then what's the value of xy?

Answer 1

x+y=6
y=6-x
x=6-y
so,
(6-x)(6-y)
6(6-y)-x(6-y)
36-6y-6x+xy
by taking common
6(6-y)-x(6-y)
(6-x)(6-y)

Answer 2

X+Y=6,

THEN,

X=6-Y AND Y=6-X,

THEREFORE,

(XY)=(6-X)(6-Y)

WE GET, XY=-36