X2 + y2 - 8x + 4y = - 4

How do you use the elimination method for this question? explain, because i really want to understand!

Find the area of an equilateral triangle with a side of 6 inches

Mr. brettler is hanging up a 5-foot tall rectangular welcome sign in the gym. he has drawn a sketch on a coordinate grid. he has the lower vertices of the sign at (9, –3) and (–6, –3). where would the upper vertices be on the grid?