r 1 16 36 144
n r 1, 1
n
196 14
k2 – 8 1
3. Let x = x(t) and y = y(t) be solutions of the
k2 – 9 0
–3 k 3 ….(II) dx
differential equations ax 0 and
From equation (I) and (II) we get dt
k 3, 2 2 2 2, 3 dy
dt
by 0 respectively, a, b R. Given that
2. The distance, of the point (7, –2, 11) from the line
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
x 6 y 4 z 8
along the line for which x(t) = y(t), is :
1 0 3
x 5 y 1 z 5 (1) log 2 2 (2) log 4 3
, is : 3
2 3 6
(1) 12 (2) 14 (3) log 3 4 (4) log 4 2
3
(3) 18 (4) 21
Ans. (2) Ans. (4)
, dx Sol. Equation of CE
Sol. ax 0
dt y – 1 = (x – 3)
dx x+y=4
adt
x
dx
x a dt
ln | x | at c
at t = 0, x = 2
ln 2 0 c orthocentre lies on the line x + y = 4
ln x at ln 2 so, a + b = 4
x
eat b
2 I1 x sin x(4 x) dx …(i)
x 2e at ….(i) a
dy Using king rule
by 0 b
dt
I1 4 x sin x(4 x) dx …(ii)
dy
bdt a
y (i) + (ii)
ln | y | bt b
t = 0, y = 1 2I1 4sin x(4 x) dx
0=0+ a
y = e–bt ….(ii) 2I1 = 4I2
According to question I1 = 2I2
3y(1) = 2x(1) I1
3e–b = 2(2 e–a) 2
I2
4
ea b 36I1
3 72
For x(t) = y(t) I2
2e–at = e–bt 5. If A denotes the sum of all the coefficients in the
2 = e(a – b)t expansion of (1 – 3x + 10x2)n and B denotes the
t
4 sum of all the coefficients in the expansion of
2
3 (1 + x2)n, then :
log 4 2 t (1) A = B3 (2) 3A = B
3
3 (3) B = A (4) A = 3B
4. If (a, b) be the orthocentre of the triangle whose Ans. (1)
vertices are (1, 2), (2, 3) and (3, 1), and
b b
Sol. Sum of coefficients in the expansion of
I1 x sin 4x x 2 dx , I2 sin 4x x 2 dx (1 – 3x + 10x2)n = A
a a then A = (1 – 3 + 10)n 8n (put x = 1)
I1 and sum of coefficients in the expansion of
, then 36 is equal to :
I2 (1 + x2)n = B
(1) 72 (2) 88 then B = (1 + 1)n = 2n
(3) 80 (4) 66 A = B3
Ans. (1)
, 6. The number of common terms in the progressions x 4 y 1 z
th Sol.
4, 9, 14, 19, ...... , up to 25 term and 3, 6, 9, 12, 1 2 3
......., up to 37th term is : x y 1 z 2
(1) 9 (2) 5 2 4 5
(3) 7 (4) 8 the shortest distance between the lines
Ans. (3)
Sol. 4, 9, 14, 19, …., up to 25th term
a b d d
1 2
T25 = 4 + (25 – 1) 5 = 4 + 120 = 124 d1 d 2
3, 6, 9, 12, …, up to 37th term
T37 = 3 + (37 – 1)3 = 3 + 108 = 111 4 0 2
st
Common difference of I series d1 = 5 1 2 3
nd
Common difference of II series d2 = 3 2 4 5
First common term = 9, and i j kˆ
their common difference = 15 (LCM of d1 and d2) 1 2 3
then common terms are
2 4 5
9, 24, 39, 54, 69, 84, 99
7. If the shortest distance of the parabola y2 = 4x from
4 10 12 0 2 4 4
the centre of the circle x2 + y2 – 4x – 16y + 64 = 0
2i 1j 0kˆ
is d, then d2 is equal to :
(1) 16 (2) 24
6 2 4
(3) 20 (4) 36
5 5
Ans. (3)
3 = | – 4|
Sol. Equation of normal to parabola
y = mx – 2m – m3 – 4 = ±3
this normal passing through center of circle (2, 8) = 7, 1
8 = 2m – 2m – m 3
Sum of all possible values of is = 8
m = –2 1
1
So point P on parabola (am2, –2am) = (4, 4)
9. If
0 3 x 1 x
dx a b 2 c 3 , where
And C = (2, 8)
a, b, c are rational numbers, then 2a + 3b – 4c is
PC = 4 16 20 equal to :
2
d = 20 (1) 4 (2) 10
8. If the shortest distance between the lines (3) 7 (4) 8
x 4 y 1 z x y 1 z 2 Ans. (4)
and is
1 2 3 2 4 5
3 x 1 x
1 1
1
6
, then the sum of all possible values of is :
Sol.
0 3 x 1 x
dx
0 3 x 1 x
dx
5
1
1 1
2 0
(1) 5 (2) 8 3 x dx 1 x dx
(3) 7 (4) 10 0
Ans. (2)
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