1+3+5+7+...+999 =
= 1+2+3+4+...+500
+1+2+3+...+499
= 2·(1+2+3+...+499) + 500
= 2·(499·500)/2 + 500
= 499·500 + 500
= 500·(499 + 1)
= 500·500
= 250.000
Yes they are correct good job
Answer:
c on edge YW
Step-by-step explanation:
The vertices of the triangle are the points where any pair of lines intersect.
We start by setting up the system

Using one of the two equations we can derive the correspondent y value:

So, one vertex is (1, 1)
We choose the other two pairs of lines to find the other vertices:


So, the three vertices are (1, 1), (2, 0), (-1, -3).
The area of a triangle is A= 1/2bh. Plugging in the values you know, 30= 1/2*12*h.
Solving for h,
30= 1/2*12*h
30= 6h
h=5
The height of the triangle is 5 units.