Answer:

Step-by-step explanation:
Move the b over to the other side to get the 2a alone.
2a=c-b
Then divide the entire equation by 2 to get a instead of 2a.


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Here's how you do it: you find all the distances between the three points and add them together to calculate the perimeter of the triangle. To calculate for the distance between two points, the formula is
d = √[(x2 - x1)² + (y2 - y1)²]
So, just take two points, assign x1 and x2 with corresponding y1 and y2, then you get the answer.
Points: D(1,4), E(3,-2), C(-3,1)
After substituting the answers would be:
DE = 6.3 units
CE = 6.7 units
CD = 5 units
Perimeter = 6.3 + 6.7 + 5
Perimeter = 18 units