Answer:
17
Step-by-step explanation:
The answer will be 20,000
Odd numbers take the form
, where
is an integer. When
, the last odd number would be 799. So we're adding

By reversing the order of terms, we have

and we can pair up terms in both sums at the same position to write

so that we are basically adding 400 copies of 800, and from there we can find the value of the sum right away:

###
We could also make use of the formulas,


We have

Remark
I think you want us to do both 3 and 4
Three
QR is 4 points going left from the y axis + 2 points going right from the y axis.
QR = 6 units long.
RT is 4 units above the x axis and 3 units below the x axis
RT = 7 units long
TS = 3 units. For this one you just go from T to S. The graph really helps you. You just need to count.
Problem 4
You need to find the area of the combined figure. You could do it as a trapezoid, which might be the easiest way. I'll do that first.
Area = (b1 + b2)*h/2
Givens
B1 = QR = 6
B2 = UT + TS = 6 + 3 = 9
h = RT = 7
Area
Area = (6 + 9)*7/2
Area = 15 * 7 / 2
Area = 52.5
Comment
You could break this up into a rectangle + a triangle
Find the area of QRTU and add the Area of triangle RTS
<em>Area of the rectangle </em>= L * W
L = RT = 7
W = QR = 6
Area = 7 *6 = 42
<em>Area of the triangle</em> = 1/2 * B * H
B = TS = 3
H = RT =7
Area = 1/2 * 3 * 7
Area = 1/2 * 21
Area = 10.5
Total Area = 42 + 10.5 = 52.5 Both answers agree.
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