Consider the function f(x)=x2e7x\displaystyle {f{{\left({x}\right)}}}={x}^{{{2}}}{e}^{{{7}{x}}}.

f(x)\displaystyle {f{{\left({x}\right)}}} has two inflection points at x = C and x = D with C < D
where C is  
and D is  

Finally for each of the following intervals, tell whether f(x)\displaystyle {f{{\left({x}\right)}}} is concave up or concave down.
(,C)\displaystyle {\left(-\infty,{C}\right)}:
(C,D)\displaystyle {\left({C},{D}\right)}:
(D,)\displaystyle {\left({D},\infty\right)}