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R-(-2,2) means the same thing dear as i have given above
if u subtrat the set (-2,2) from the set of real numbers R u wud get the same thing ie.(-infinty,-2]U[2,infinity)
i hope its clear now
tell me if u still have doubt

i think it shud be c) am i right

domain wud be (-infinity,-2]U[2,infinity)
first assume let x>0
|x|=x
so for sqrt a to be defined thye given equatn shud be >0
x^2-x-2>0
x=(-infinty -1]U[2,infinity)
but since x>0 so solution wud be [2,infinity)
similarly whn x<0
eqn wud be x^2+x-2
this is >0 for x =(-infinity,-2]U[1,infinty)
but x<0
so solution is (-infinty,-2]
so domain wud be (-infinity,-2]U[2,infinity)
nudge me if u have any doubt
rate if useful

45 b)
as copper is a conductor whose resistance increases on inc temp and Ge is a semiconductor whose resistance decreases on inc temp

35 a)

50 a)

21 c)
27.c)

25 b)

44.a)

36. c) its the reverse of wat is given

18 c)

thanx but i dnt think it was tht tuff was it??

19.c) d)

CsCl has bcc structure so coordination is 8

so 1st two options are wrong

for NaCl the relation is r Na+ r Cl= a/2

so frm here a comes out to be 552

and abt c u know that the atom at the corner is shared by 8 unit cells similarly that on face is shared by 2 unit cells so c is correct

nudge me if u have any doubt

rate if useful

17.the answer is HgS

sorry edited

NaCl has formula Na4 Cl4

c for the diff values of r

r=1

a,b = 1,4/3

for r=2

c,d=2,8/3

for r=3

e,f= 3,12/3

.

.

.

similarly the last pair wud be 120,480/3

so b+d+f....=4/3[1+2+3+...120]

a+c+e....=1+2+3+...120

so b+d+f.... - (a+c+e...)=

4/3(120)(121)/2 - 120(121)/2 [using sum of n terms]

=1/3(120)(121)/2

=2420