There are three things you have to know:
- A function is convex when its second derivative
- A function is concave when it second derivative
- The derivative of a power,
, is 
So, the first derivative is
and the second derivative is
This implies that the second derivative of a parabola is constant, and of course that 2 doesn't change the sign of 
.
The two numbers are very near 7200 and 300. The sum of those is a good estimate of your sum:
... 7200 + 300 = 7500
_____
If you're taught methods of addition that include "make a ten" or "make a hundred", you know you can "borrow" a 1 from 7203 (making it 7202) and loan that 1 to 299 to make it 300. Now, you know your sum is exactly 7202+300 = 7502, with no estimation necessary.
Answer:
X=3
Step-by-step explanation:
7 x 1 = 7
7 x 2 = 14
7 x 3 = 21
You add seven to the last answer to get your next one.
#1)
The area of the rectangular section in the middle is given by 15(12)=180ft².
The area to the right can be broken into a rectangle, whose area is 8(10)=80ft², and a triangle, whose area is (1/2)(5)(8)=20ft².
The area to the left can be represented as a rectangle minus a triangular area. The dimensions of the complete rectangle would be 15(5)=75ft². However it is missing a triangle at the top whose area would be (1/2)(5)(5)=12.5ft². Thus we have 180+80+20+75-12.5=242.5ft².
#2)
The area of the weight room is given by 28(30)=840ft². The area of the Dance Studio is given by 33(42)=1386. There is a corner that is counted twice, however. The area of this corner is 14(14)=196ft². Our total area is then 840+1386-196=2030ft².
{5x + 4y = -30
{3x - 9y = -18 | : 3
{5x + 4y = -30
{x - 3y = -6 | + 3y
{5x + 4y = -30
{x = 3y - 6
{5(3y - 6) + 4y = -30
{x = 3y - 6
{15y - 30 + 4y = -30 | + 30
{x = 3y - 6
{19y = 0 | : 19
{x = 3y - 6
{y = 0
{x = 3 · 0 - 6
{y = 0
{x = -6
