How do you write x² − 8x in vertex form?

  side lengths are 6, 12, 12, 9, 9

Step-by-step explanation:

The perimeter is the sum of the lengths of the sides:

  x + 2x + 2x + (x+3) + (x+3) = 48

  7x +6 = 48 . . . . collect terms

  7x = 42 . . . . . . .subtract 6

  x = 6 . . . . . . . . . divide by 7

Substitute this value into the expressions for the side lengths:

  x = 6

  2x = 12

  x+3 = 9

The side lengths are 6, 12, 12, 9, 9.