The area of the rectangular roof shingle is 70 inches
First term: a1 = 151
common difference: d = -14 (we decrease by 14 each time, eg, 151-14 = 137)
nth term of this arithmetic sequence is...
an = a1+d(n-1)
an = 151+(-14)(n-1)
an = 151-14n+14
an = -14n+165
This will be used in the formula below
Sn = n*(a1+an)/2
<span>Sn = n*(151+(-14n+165))/2
</span><span>S26 = 26*(151+(-14*26+165))/2 ... replace every n with 26
</span>S26 = -624
The final answer here is choice C) -624
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3√24 + 2√3(√3-2√18) =
3(√(4*6) + 2√3( √3-2√(2*9)) =
3*2√6 + 2√3 ( √3 - (2*3) √2) =
6√6 + 2√3(√3 - 6√2) =
6√6 + 6 - 12√3*√2 =
6√6 + 6 - 12√(6) =
6 - 6√6 = 6(1-√6)
