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# Find the sum of the first 20 terms of the arithmetic sequence whose gen form is an=23+7n​

• Réponse publiée par: cbohol56

Hello !!

Find the first term.

An = 23 + 7n

A1 = 23 + 7(1)

A1 = 23 + 7

A1 = 30

Find the 20th term.

An = 23 + 7n

A20 = 23 + 7(20)

A20 = 23 + 140

A20 = 193

Find the sum of the first 18 terms of the sequence.

Sn = (n/2) × (A1 + An)

S20 = (20/2) × (30 + 193)

S20 = 10 × 223

S20 = 2230

Final result : the sum of the first 20 terms is 2230.

I hope I have collaborated !

• Réponse publiée par: meteor13

1 965 is the 20th place in arithmetic

Step-by-step explanation:

an = a1 + (n-1) d

a20 = 122 + (20-1) 97

a20 = 122 + (19) 97

a20 = 122 + 1 843

a20 = 1 965

*Basta ganito yung formula ikaw na bahala mag mag-compute ng total. :)

• Réponse publiée par: cbohol56

1290

Step-by-step explanation:

Given:

n = 20

A1 = 3

An = 83

Formula:

Substitute and calculate.

• Réponse publiée par: nelspas422

19nt

Step-by-step explanation:

• Réponse publiée par: nelspas422

C.200

anong subject yan

• Réponse publiée par: reyquicoy4321

B. 1100

Step-by-step explanation:

• Réponse publiée par: calmaaprilgrace

B.780

Step-by-step explanation:

n=20,a1= -24,an=102

Sn=n/2(a1+a2)

S20=20/2(-24+102)

S20=10(78)

S20=780

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• Réponse publiée par: elaineeee

It's just a substitution:

SOLUTION:

a1 = 23 + 7(1)

a1 = 30

Arithmetic Sequence: 30, 37, 44, 51, 58, 65, 72, 79, 86, 93, 100, 107, 114, 121, 128, 135, 142, 149, 156, 163.

FORMULA: Sn = n(a1 + an) / 2

S20 = 20 (30 + 163) / 2

= 10 (193)

= 1, 930

ANSWER: The sum of the first 20 terms is 1, 930.

• Réponse publiée par: dorothy13

The answer is letter B. - 730

FIRST TERM a1= - 122;

NUMBER OF TERMS n=20;

COMMON DIFFERENCE d=9

Sn= n/2 [2a1 + (n-1) d]

S20= 20/2 [2(-122) + (20-1) 9]

S20= 10 [-244 + 171]

S20= 10 (-73)

S20= - 730

• Réponse publiée par: hannahleigh

The sum of the first 20 terms of the arithmetic sequence is 780.

Step-by-step explanation:

Given:   ,   ,

Formula:

Substitute the given in the formula to find the sum of the first 20 terms

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Find the sum of the first 20 terms of the arithmetic sequence whose gen form is an=23+7n​...