Answer:
480
Step-by-step explanation:
Sn = n÷2 × (2a + (n-1)d)
n = 20 a = -14 d = 4
S20 = 10 × (-28 + 19 × 4) = 480
Perfect squares are n² where n is a whole number
whole numbers are like 0,1,2,3,4,5,6, etc
no decimal or fractions
we can do that be looking at the perfect squares we know
2²=4
3²=9
4²=16
5²=25
6²=36
7²=49
8²=64
etc
so we see 47 is between 6² and 7²
therefor, for n²=47, n is between 6 and 7 and is therfore not a whole number
that makes 47 not a perfect square
Given:
15% of its height each day
27 inches on day 10.
How tall was it yesterday?
27 represents 115% of the height yesterday. So we divided 27 by 115% to get yesterdays height.
27 ÷ 115% = 23.48 inches.
The plant was 23.48 inches tall yesterday.
To check:
23.48 x 15% = 3.52 inches
23.48 + 3.52 = 27 inches
(2h – 3)(3h + 4) is the same thing as
2h(3h + 4) - 3(3h + 4)
6h^2 + 8h - 9h - 12
6h^2 - h - 12
Answer B.
