Hi there!
The formula to find the are of a circle is :
a =
r²
The formula to find the circumference of a circle is :
c = 2
r
In order to use the area formula, you need to figure out what the radius (r) is.
If we solve for "r" in the circumference equation, we have :
r = c ÷ (2
)
Now we use this to replace "r" in the area formula :
a =
( c ÷ (2
))²
When we simplify this we get :
a = c² ÷ 4
Now you can put your value of "c" into this equation and find "a".
*Remember,
is about 3.1416.
Solving for "a" :
a = c² ÷ 4
a = 28² ÷ 4
28² = 28 × 28 = 784
a = 784 ÷ 4
4
= 4 ×
= 12.56637061435917
a = 784 ÷ 12.56637061435917
a = 62.38873769202297cm²
You need to round to the nearest square centimeter, which means that you need to round to the nearest whole number :
a = 62cm²
There you go! I really hope this helped, if there's anything just let me know! :)
1.

2.
<u> </u><u>Sub (1, -5) into equation to find '</u><em><u>b'</u></em><u />
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4.
=(3a-4a-3a)+(2b+6b-2b)+(-7c+9c-7c)
=-4a+6b-5c #
I think it is D 1.8. hope this help's