Equation of an ellipse
→having center (0,0) , vertex (
and covertex 
and focus 
is given by:
As definition of an ellipse is that locus of all the points in a plane such that it's distance from two fixed points called focii remains constant.
Consider two points (a,0) and (-a,0) on Horizontal axis of an ellipse:
Distance from (a,0) to (c,0) is = a-c = 
Distance from (-a,0) to (c,0) is = a + c = 
a -c + a +c
= a + a
= 2 a →(Option A )
Answer:52
Step-by-step explanation:
Given
one-fifth of the plants in a garden are grape tomato plant
two-ninth of the plants in the garden are cherry tomato plants
Also there are 18 grape tomato and 20 cherry tomato plants.
Let Total plants be x
Then Grape tomato plants 
x=90
thus there are total of 90 plants
also grape tomato+cherry tomato=18+20=38
Thus there are 90-38=52 remaining plants.
I would choose the answer D
Answer:
Step-by-step explanation:
the formula for the circumference of a circle is 2rπ
the formula for the area of a circle is (r^2)π
the formula for the diameter of a circle is 2r
π=3.14
---------------------------------------------------------------
1. diameter =2r. since diameter=24, r=12
2. circumference=2rπ. since circumference = 314. 314=2rπ r=49.9746
3. circumference=2rπ area=(r^2)π
since r=7, circumference=14π=43.98229 since r=7, area is 49π=153.9380
4. Since the diameter is 20 the radius is 10. so just insert it into the formulas as before: circumference=20π=62.8318 and area=100π=314.15926
5. the formula for the diameter is 2r=d 2(18)=d, 36=d
6. 2rπ=circumference = 2(5)π=10π=31.415926
Hope that helps :)
