two sides of an equilateral triangle measure (y+10) and (y^2 (-2)). if the perimeter of the triangle is 21 units what is the value of y?

y = - 3

Step-by-step explanation:

Each side of an equilateral triangle will have a length that is 1/3 the perimeter. This triangle has sides of length 21/3 = 7, so ...

y + 10 = 7

y = 7 - 10

y = - 3

This is consistent with the other given side measure ...

y^2 - 2 = (-3) ^2 - 2 = 9 - 2 = 7