Let Z be the set of all integers, and consider the sets
X={(x,y):x2+2y2=3, x,y∈Z} and
Y = \{(x,y) : x > y,\ x, y \in \mathbb{Z} \}.
Then the number of elements in X∩Y is
Explanation
X={(x,y):x2+2y2=3}
x2+2y2=3
⇒3x2+3/2y2=1 (ellipse form)
Y = \{(x, y) : x > y,\ x, y \in \mathbb{Z} \}
Now find integer solutions for x2+2y2=3:
Try small integers:
- (1,1):12+2(1)2=1+2=3
- (−1,1):1+2=3
- (1,−1):1+2=3
- (−1,−1):1+2=3
So, X={(1,1),(−1,1),(1,−1),(−1,−1)}
Now apply the condition x > y from set Y:
- (1,1):x=y
- (-1,1): x < y
- (1,-1): x > y
- (−1,−1):x=y
So, X∩Y={(1,−1)}
**Option (a)**
Explanation
X={(x,y):x2+2y2=3}
x2+2y2=3
⇒3x2+3/2y2=1 (ellipse form)
Y = \{(x, y) : x > y,\ x, y \in \mathbb{Z} \}
Now find integer solutions for x2+2y2=3:
Try small integers:
- (1,1):12+2(1)2=1+2=3
- (−1,1):1+2=3
- (1,−1):1+2=3
- (−1,−1):1+2=3
So, X={(1,1),(−1,1),(1,−1),(−1,−1)}
Now apply the condition x > y from set Y:
- (1,1):x=y
- (-1,1): x < y
- (1,-1): x > y
- (−1,−1):x=y
So, X∩Y={(1,−1)}
**Option (a)**