Question 1153139
The perimeter is the sum of the lengths of each side:<br>

AB = {{{ sqrt((7-1)^2+(-1-5)^2) = sqrt(36+36) = 6sqrt(2) }}} ... or approx 8.485
BC = {{{ sqrt((-2-7)^2+(-2-(-1))^2) = sqrt(81+1) = sqrt(82) }}} ... approx 9.055
CA = {{{ sqrt((1-(-2))^2+(5-(-2))^2) = sqrt(9+49) = sqrt(58) }}} ... approx 7.616
<br>
Adding the three lengths (and assuming my math is correct):<br>
  perimeter = 25.156 units