Hello from MrBillDoesMath!
Answer:
225
Discussion:
Sum ( 2n - 1) from n = 1 to 15
= Sum(2n) - Sum(1) from n = 1 to 15
= 2 Sum(n) - Sum(1) from n = 1 to 15
= 2* 15(15+1)/2 - (1 + 1 + .. + 1)
The first value comes from the fact that the sum of the first n integers is n(n+1)/2. The latter value sums 15 1's.
= 2 * 15 * 16/2 - 15 => 2/2 = 1
= 15*16 - 15 => 15*16 = 240
= 240 - 15
= 225
Thank you,
MrB
<span> 5 – 6x = 8x + 17
</span>⇔ 5 - 17 = 8x + 6x
⇔ -12 = 14x
⇔ x = -6/7
All triangles are similar.
.. x/3 = 27/x
.. x^2 = 81
.. x = 9
.. y = √(x^2 -3^2) = √72
.. y = 6√2