Answer:
20
Step-by-step explanation:
You have to fill in 6 slots _ _ _ _ _ _.
Since first digit must be 4, there is only 1 way to fill in the 1st slot.
with the 5 slots, we fill in the 6s first, 3 of them.
So we have 5 options and 3 items to fill, (5 choose 3).
Then 2 ways to fill 1 and 1 way to fill 5. (It doesn't matter if you pick 5 or 1 first).
So it becomes (5C3) * (2C1) *(1C1)
= 1 * 5!/(3!)(5-3)! * (2) * 1
= 20
Answer:
as the point (8,0) lies on the x-axis (east) and the bearings are defined with respect to south or north according to the rotation as well. so here the angle is 90 and the directions are N90E or S90W
-2x+ 12 = x^2 +16
-2x -4 = x^2
-4= x^2 + 2x
-4= 3x
-4/3 = 3/3x
-1.333 (repeated) = x
1
:x
2
+y
2
−6x−9y+13=0
(x−3)
2
+(y−
2
9
)
2
−9−
4
81
+13=0
(x−3)
2
+(y−
2
9
)
2
=
4
65
Here,
r
1
=
2
65
C
1
=(3,
2
9
)
Equation of another circle-
S
2
:x
2
+y
2
−2x−16y=0
(x−1)
2
+(y−8)
2
−1−64=0
(x−1)
2
+(y−8)
2
=65
Here,
r
2
=
65
C
2
=(1,8)
Distance between the centre of two circles-
C
1
C
2
=
(3−1)
2
+(8−
2
9
)
2
C
1
C
2
=
4+
4
49
=
2
65
∣r
2
−r
1
∣=
∣
∣
∣
∣
∣
∣
65
−
2
65
∣
∣
∣
∣
∣
∣
=
2
65
∵C
1
C
2
=∣r
1
−r
2
∣
Thus the two circles touches each other internally.
Since the circle touches each other internally. The point of contact P divides C
1
C
2
externally in the ratio r
1
:r
2
, i.e.,
2
65
:
65
=1:2
Therefore, coordinates of P are-
⎝
⎜
⎜
⎜
⎜
⎜
⎛
1−2
1(1)−2(3)
,
1−2
1(8)−2(
2
9
)
⎠
⎟
⎟
⎟
⎟
⎟
⎞
=(5,1)
Therefore,
Equation of common tangent is-
S
1
−S
2
=0
(5x+y−6(
2
x+5
)−9(
2
y+1
)+13)−(5x+y−2(
2
x+5
)−16(
2
y+1
))=0
2
−6x−9y−13
+x+8y+13=0
4x−7y−13=0
Hence the point of contact is (5,1) and the equation of common tangent is 4x−7y−13=0.
