Topic Question Set


Q 21 :

Let S1={xR-{1,2}:(x+2)(x2+3x+5)-2+3x-x20} and S2={xR:32x-3x+1-3x+2+270}. Then, S1S2 is equal to

  • (-,-2](1,2)

     

  • (-,-2][1,2]

     

  • (-2,1](2,)

     

  • (-,2]

     

(2)

For S1 we have(x+1)(x2+3x+5)x2-3x+20

x(-,-2)(1,2)

For S2 we have

3x(3x-3)-32(3x-3)0

For S2,  x[1,2]

(-,-2)[1,2]



Q 22 :

Let i=150Xi=i=1nYi=T, where each Xi contains 10 elements and each Yi contains 5 elements. If each element of the set T is an element of exactly 20 of sets Xi's and exactly 6 of sets Yi's, then n is equal to

  • 15

     

  • 50

     

  • 45

     

  • 30

     

(4)

i=150Xi=i=150Yi=T    

    n(Xi)=10, n(Yi)=5

So, i=150Xi=500,    i=150Yi=5n

50020=5n6

n=30