Let S= \x :( 3+ 2)x+( 3- 2)x=10 \. Then the number of elements in S is :
- 4
- 0
- 2
- 1
Answer
(3) 2
Solution
∵ ( 3+ 2)( 3- 2)=1, let t=( 3+ 2)x>0 ⇒ ( 3- 2)x= 1t
t+ 1t=10 t2-10t+1=0 t=5 2 6
5+2 6=( 3+ 2)2, 5-2 6=( 3+ 2)-2
x=2 or x=-2 ⇒ S has 2 elements
Answer: (3)