[填空题]
$\text { Let } f(x)=2 x^{2}-5 x+7 \text {. The line } L \text { intersects } f \text { at } \mathrm{P}(3,10) \text { and is perpendicular to the tangent to the curve of } f \text { at } \mathrm{P} \text {. Find the equation of } L \text { in the form } y=m x+c \text {. }$
