I Need help with a question. (Find a negative real number such that the square of the sum of the number and 2 is equal to 36.)

Let a be the number...and we have

(a + 2)^2  = 36      take both roots

a + 2  = ± √36

a + 2 =  ± 6

So either

a + 2  = 6   →   a  = 4      .....or.....

a + 2  = -6   →   a  = - 8        and that's our answer