[tex]~~~~~~~~~~~~\textit{quadratic formula} \\\\ \stackrel{\stackrel{a}{\downarrow }}{25}p^2\stackrel{\stackrel{b}{\downarrow }}{-40}p\stackrel{\stackrel{c}{\downarrow }}{+16}=0 \qquad \qquad p= \cfrac{ - b \pm \sqrt { b^2 -4 a c}}{2 a} \\\\\\ p= \cfrac{ - (-40) \pm \sqrt { (-40)^2 -4(25)(16)}}{2(25)}\implies p=\cfrac{40\pm \sqrt{1600-1600}}{50} \\\\\\ p=\cfrac{40\pm\sqrt{0}}{50}\implies p=\pm\cfrac{40}{50}\implies p=\pm\cfrac{4}{5}[/tex]
