Help me do the ones marked in red.

  2. "two thirds of the fourth power of r"

  4.  n + 14

  6.  7 +11n

  8.  (2/5)n^2

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  7.  28

  8.  1/5

Step-by-step explanation:

2. "two thirds of the fourth power of r"

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4. "sum" means the listed items are added. You can use any convenient variable to represent "a number." I often use n for number.

  n + 14

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6. "7 more than" means 7 is added to whatever follows. "11 times a number" means the number is multiplied by 11.

  7 + 11n

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8. "of" means "times". The square of a number is that number to the power of 2.

  (2/5)n^2

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7 & 8 (evaluation). Your calculator can do this. (If not, get one that can.) Note that parentheses are needed around numerators and denominators and anything else that must be treated as a single value.

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb