Finding the minimum value of the square of a + 2a-1

Finding the minimum value of the square of a + 2a-1

a²+2a-1=(a+1)²-2
∵(a+1)²≥0
∴ a+1)²-2≥-2
That is to say, the minimum value of a & # 178; + 2a-1 is - 2