Let f be a function where f(x)=x2+3 Rachel wants to transform the graph of f by stretching it horizontally by a factor of 5. She says that an equation for her new function p in terms of f is...

Let f be a function where f(x)=x²+3

Rachel wants to transform the graph of f by stretching it horizontally by a factor of 5. She says that an equation for her new function p in terms of f is p(x)=f(5x) which means p(x)=(5x)²+3. Is Rachel's equation correct? Explain or show your reasoning.