Solve the quadratic equation by factoring.

$\displaystyle {4}{a}^{{2}}-{49}={0}$

$\displaystyle {a}=$Preview Question 6  

Write your answers as a list of integers or reduced fractions, with your answers separated by (a) comma(s). For example, if you get $\displaystyle {4}$ and $\displaystyle -\frac{{2}}{{3}}$ as your answers, then enter 4,-2/3 in the box.