Question 826139
The line through (-1,-1)and (2,0) has slope, {{{(9-(-1))/(2-(-1))=highlight_red(10/3)}}}.
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The desired line perpendicular to it must have slope {{{m(10/3)=-1}}},
{{{highlight_red(m=-(3/10))}}}.


Using point-slope form for a linear equation and the required point and slope, {{{-(3/10)(x-1)=y-3}}}
{{{y=-(3/10)x+3/10+3}}}
{{{highlight(y=-(3/10)x+3&3/10)}}}