Vertical stretch of function:
Suppose, we are given to vertically stretch any function f by 'a' units
so, we multiply y-value by 'a'
assume
new function is g(x)
so, we get
![g(x)=a* f(x)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/vg37h51kl8jlm7h7c4sucej16py24e5hi9.png)
now, we are given
The graph of function g is a vertical stretch of the graph of function f by a factor of 3
so, a=3
so, we get
![g(x)=3f(x)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/mp3ahqtpgb35dp2c9lt36lcf17phffhsc5.png)
option-A.........Answer