We can represent the horizontal shift of a quadratic equation by adding or subtracting the constant h to the function
[tex]\begin{gathered} f(x)=a(x-h)^2+k \\ \text{where} \\ h\text{ is the horizontal shift} \end{gathered}[/tex][tex]\begin{gathered} \text{The function }f(x)\text{ has a default values of} \\ a=1 \\ h=0 \\ k=0 \\ \\ \text{A shift to the left of 3 units means that we will have }h=-3\text{ that means} \\ \\ F(x)=(x-(-3))^2 \\ \\ \text{Simplify},\text{ and we get} \\ F(x)=(x+3)^2 \end{gathered}[/tex]