[tex]10p^2 +20=1490[/tex]
[tex]
10p^2=1490-20
[/tex] [tex]Subtract \ 20 \ from \ both \ sides[/tex]
[tex]10p^2=1470
[/tex]
[tex]p^2= \dfrac{1470}{10} [/tex] [tex]Divide \ both \ sides \ by \ 10[/tex]
[tex]p^2=147[/tex]
[tex]p=+ \sqrt{147} [/tex] [tex]Take \ the \ square \ root \ of \ both \ sides[/tex]
[tex]p=+7 \sqrt{3} [/tex]