JAMB - Mathematics (2009 - No. 8)
If x = {n\(^2\)+1:n is a positive integer and 1 \(\leq\) n \(\leq\) 5},
Y = {5n:n is a positive integer and 1 \(\leq\) n \(\leq\) 5}, find x \(\cap\) y.
Y = {5n:n is a positive integer and 1 \(\leq\) n \(\leq\) 5}, find x \(\cap\) y.
{5,10}
{5, 10, 15}
{2, 5, 10}
{5, 10, 15, 20}
Explanation
X = {n(^2\)+1:n is a positive integer and 1 \(\leq\) n \(\leq\) 5}
Implies X = {2, 5, 10, 17, 26} i.e. put n= 1, 2, 3, 4 and 5
Y = {5n:n is a positive integer and 1 \(\leq\) n \(\leq\) 5}
Put X = 1, 2, 3, 4, and 5
Y = {5, 10, 15, 20, 25}
X \(\cap\) Y = {2, 5, 10, 17, 26} \(\cap\) {5, 10, 15, 20, 25}
= {5, 10}
Implies X = {2, 5, 10, 17, 26} i.e. put n= 1, 2, 3, 4 and 5
Y = {5n:n is a positive integer and 1 \(\leq\) n \(\leq\) 5}
Put X = 1, 2, 3, 4, and 5
Y = {5, 10, 15, 20, 25}
X \(\cap\) Y = {2, 5, 10, 17, 26} \(\cap\) {5, 10, 15, 20, 25}
= {5, 10}
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