$a_n=a_1+d(n-1)\\\\a_8=a_1+d\cdot7\\\\a_{20}=a_1+d\cdot19\\\\a_{20}-a_8=a_1+19d-(a_1+7d)=12d\\\\56-20=2d\\\\12d=36\\\\d=3\\\\\\ a_1+3\cdot7=20\\\\a_1=20-21=-1$

6 0

2 years ago

What is the area of the circle? Round to the nearest whole number, if necessary.

Alla [95]

Well idk what the numbers are, but the formula to find the are is 3.14(pi) x r^2

7 0

2 years ago

3. What is the radius of a circle whose area is 64π cm squared?

nataly862011 [7]

Answer:

Area = 64π

Area \: = \pi {r}^{2}Area=πr

64 \: \pi \: = \pi {r}^{2}64π=πr

{r}^{2} = \dfrac{64\pi}{\pi}r

64π

{r}^{2} = 64r

=64

r \: = \: \sqrt{64} = 8r=

Radius = 8 units

Finding the Diameter -

Diameter = Radius x 2 = 8 x 2 = 16 .

\bold{Diameter \: is \: 16 \: units}Diameteris16units

8 0

2 years ago