how is -3+2(-1+4)^2 come out to equal 15,,,, i am always getting -9

PEMDAS

Parentheses first

Exponent second

Multiply and Divide third (doesn't matter which of these precedes the other)

Addition and Subtraction fourth (again doesn't matter which of these precedes the other)

So:

-3 + 2*(-1+4)^2     Parentheses

-3 + 2*3^2              Exponent

-3 + 2*9                  Multiplication

-3 + 18                    Addition

15