Question

12

y= x2 + x-2
x+ y=1
If (x, y) is a solution of the system of equations
above, which of the following is a possible value of
xy?
A) 7
B 1
C) -1
D) -12​

Answer 1

D,xy=-12

Explanation:

y=x²+x-2

x+y=1

or x+x²+x-2=1

x²+2x-3=0

x²+3x-x-3=0

x(x+3)-1(x+3)=0

(x+3)(x-1)=0

either x=-3

or x=1

when x=-3

x+y=1

-3+y=1

y=1+3=4

one solution is (-3,4)

xy=-3×4=-12

if x=1

1+y=1

y=0

second solution is (1,0)

xy=1×0=0