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Welcome to ICOME Quiz Corner

Q1. Evaluate
(x + 2)3 - 8/ x

Solution.
y = x + 2 , x → 0

x = y - 2, y → 2

=
y3 - 23/y - 2


= 3(2)2 = 12
Solution

Q2. Find
log x - log 5/ x - 5

=
log
x/ 5
/x - 5
=
log(1 +
x/ 5
- 1)
/ x - 5


log(1 +
x - 5/5
)
/(
x - 5/ 5
) . 5
=
1 /5
Solution

Q3. Evaluate
sin x - sin a /x - a

Solution.
Using D' hospital law derive the function

cosx /1
= cos a
Solution

Q4. Evaluate
sin x . cos x /4x

Solution.
1/4
(
sin x /x
)(cos x) =
1/4
(
sin x /x
) . (cos x)

=
1/4
Solution

Q5. Evaluate
9x cosx - 4sinx /5x + 3tanx

Solution.
=
(
9x cosx - 4sinx /x
)
/ (
5x + 3tanx /x
)


=
9cosx -
4sinx /x
/5 +
3tanx /x


=
9 - 4/5 + 3
=
5/8
Solution

Q6. Evaluate
xx /(1 + x)x

Solution.
1/ (1 +
1 /x
)x
=
1/e


(∴ (1 + x)1/x = e)
Solution

Q7. Evaluate
1 /x2
(1 + 2 + 3 + --------+ x) .

Solution.
=
1 /x2
∑ x =
x(x + 1) /2x2
=
x + 1 /2x


(
x /2x
+
1 /2x
) =
1/2
+
1 /2x
=
1/2
Solution

Q8. Find
x + x2 + x3 + ----------+ xn - n /x - 1

Solution.
=
(x - 1) + (x2 - 1) + (x3-1) + ----------+ (xn - 1) /x - 1


{
x - 1 /x - 1
+
x2 - 1/x - 1
+
x3-1/x - 1
+ ------ +
xn - 1/x - 1
}

1 + 2 + 3 + -------- + n

=
n(n + 1) /2


(∴
xn - an /x - a
= nan - 1)
Solution

Q9. Evaluate
5x - 1 /√(1 + x) - 1

Solution.
=
5x - 1 /√(1 + x) - 1
x
√(1 + x) + 1/√(1 + x) + 1


=
5x - 1 /x
(√(1 + x) + 1)

= (log 5) . 2 = 2 log 5
Solution

Q10. Evaluate
(ex + e-x - 4)(x2 - 3x + 2) /x - 1

Solution.
=
(ex + e-x - 4)(x - 1)(x - 2) /x - 1


= (ex + e-x - 4)(x - 2)

= (e +
1/e
- 4)(-1)

= - (
e2 + 1/e
- 4)
Solution