Is this arithmetic, geometric or neither? If arithmetic, what is the difference? If geometric, what is the ratio?
1/2 + 5/6 + 7/6 + 3/2 + 11/6...
Arithmetic with d=1/3
Is this arithmetic, geometric or neither? If arithmetic, what is the difference? If geometric, what is the ratio?
1/3 + 2/15 + 4/75 + 8/375 + ...
Geometric, r = 2/5
Find the sum:
-12 + -7 + -2 + ... + 183
tn = -12 + (n-1)(5) S40 = 40(-12 + 183)/2
183 = -12 + 5n -5 = 20(171)
n=40 = 3,420
Expand 10
∑ 3n/(n+1)
n=5
3(5)/(5+1) + 3(6)/(6+1) + 3(7)/(7+1) + 3(8)/(8+1) + 3(9)/(9+1) + 3(10)/(10+1)
= 15/6 +18/7 +21/8 + 24/9 + 36/10 + 30/11
What is the 10th row of Pascal's Triangle?
1 10 45 120 210 252 210 120 45 10 1
Find the 20th term in the series
1 + 16 + 31 + 46 + ...
tn = 1 + (n-1)15
=15n-14
t20 = 15(20)-14 = 286
Find the 8th term in the series: 2 + 10 + 50 + 250 + ....
tn = 2(5)n-1
t8 = 2(5)7 =156,250
Find the sum of the first 100 terms of the series:
4 + 7 + 10 + 13 + ...
t100 = 4 + (100-1)(3)
= 301
S100 = 100(4 + 301)/2
= 50(305) = 15,250
Write in sigma notation:
1 + 3 + 5 + ... + 199
100 tn = 1 + (n-1)2
∑ 2n-1 = 1 + 2n - 2 = 2n - 1
n=1 2n - 1 = 199
2n = 200
n = 100
Expand (a + b)7
a7 + 7a6b + 21a5b2 + 35a4b3 + 35a3b4 + 21a2b5 + 7ab6 + b7
Find the formula for the nth term and then find the 101st term:-2, -11, -20, ...
tn = -9n + 7
t101 =-902
Find the formula for the nth term and then find the 10th term: 8, 12, 18, 27, ...
tn = 8 *(3/2)n-1
t10 = 8 * (3/2)9 = 307.55
Find the sum of the first 9 terms of
tn = -960(-3/2)n-1
S9 = -960(1 - (-3/2)9) / 1 - (-3/2)
= -960(1 + 3/29) / 5/2
= -384(1 + 3/29) = -15,146.25
Write in sigma notation: 6 -12 + 24 - ... -192
6 tn = 6(-2)n-1
∑ 6(-2)n-1 -192 = 6(-2)n-1
n=1 -32 = (-2)n-1
(-2)5 = (-2)n-1
6 = n
Expand (3x - y)5
(3x)5 + 5(3x)4(-y) + 10(3x)3(-y)2 + 10(3x)2(-y)3 + 5(3x)(-y)4 + (-y)5
= 243x5 - 405x4y + 270x3y2 - 90x2y3 + 15xy4 - y5
Find the position of the last term:
25 + 33 + 41 + ... + 145
tn=25 + (n-1)8 = 25 + 8n -8 = 17 + 8n
17 + 8n = 145
8n = 128
n=16
Find the position of the last term in the series: 3 + 6 + 12 + 24 + ... + 384
tn = 3(2)n-1
384 = 3(2)n-1
128 = 2n-1
27 = 2n-1
n=8
Find the sum of the series: 1,500 + 1,550 + 1,600 + 1,650 + ... 4,000
tn = 1,500 + (n-1)50 S51 = 51(1,500 +4,000)/2
4,000 = 1,500 + 50n - 50 = 51(2,750)
2,550 = 50n = 140,250
51 = n
Write in sigma notation: 1 + 1/2 + 1/3 + 1/4 + ... + 1/47
47
∑ 1/n
n=1
Find the 4th term (k=3) for the expansion of
(x2 - 3y)18
18!/(18-3)!3! (x2)18-3(-3y)3
= 18*17*16*15!/15!*6 (x2)15(-27y3)
= 3*17*16*(-27) x30y3
= -22,032x30y3
A pile of bricks has 85 bricks in the bottom row, 79 bricks in the second row, 73 bricks in the third row, and so on until there is only 1 brick in the top row.
a. How many bricks are in the 12th row?
b. How many rows are there in all?
a. 85 + 79 + 73 + ... + 1 b. 1 = 91 - 6n
tn = 85 + (n-1)(-6) = 91 - 6n -90 = -6n
t12 = 91-6(12) = 19 bricks n = 15 rows
A new pair of running shoes costs $10 now. They double in price every year. How much will they cost in 14 years?
t14 = 10*(2)n-1 = 10*(2)14-1 = $81,920
Find the sum of:
64/9 + 16/3 + 4 + 3 + ...
S∞ = (64/9)/(1 - 3/4) r = 3/4
= (64/9)/(1/4)
= 28.4
Write in sigma notation:
1/3 + 4/6 + 9/9 + 16/12 + 25/15 + ... 169/39
13
∑ n2/3n
n=1
Find the first 4 terms of the expansion of (x2 + 3y)15
k=0 --> (x2)15 = x30
k=1 --> 15(x2)14(3y) = 45x28y
k=2 --> 15!/(15-2)!2! (x2)13(3y)2 = 945x26y2
k=3 --> 15!/(15-3)!3! (x2)12(3y)3 = 12,285x24y3
x30 + 45x28y + 945x26y2 + 12,285x24y3