Question

Arithmetic sequence help!!!!

Answer 1

a₅ = 10

a₁₀ = 20

a₁₅ = x

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Note that from a₅ to a₁₀, there is a addition of 10. This means that for every x(₅) jump, you add 10 to the whole number.

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So in this case:

a₁₀ = 20

a₁₅ = x

a₁₀ (+₅) = 20 (+10)

a₁₅ = 20 + 10

a₁₅ = 30

Note that: a₁₅ = x = 30

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x = 30, or (A) is your answer

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hope this helps

Answer 2

$a_5=10;\ a_{10}=20\\\\a_n=a_1+(n-1)d\\\\a_{10}-a_5=5d\\\\5d=20-10\\5d=10\ \ \ |:5\\d=2\\\\a_1=a_5-4d\\\\a_1=10-4\cdot2\\a_1=10-8\\a_1=2\\\\a_{15}=2+(15-1)\cdot2\\a_{15}=2+14\cdot2\\a_{15}=2+28\\a_{15}=30$

Answer: 30