Question 324048
For a triangle,
{{{A=(1/2)bh}}}
{{{A=(1/2)(4+2h)h=42}}}
{{{h(2h+4)=84}}}
{{{2h^2+4h-84=0}}}
{{{h^2+2h-42=0}}}
Use the quadratic formula,
{{{h = (-2 +- sqrt( 2^2-4*1*(-42) ))/(2*1) }}} 
{{{h = (-2 +- sqrt( 4+168 ))/2 }}} 
{{{h = (-2 +- sqrt( 172))/2 }}} 
{{{h = (-2 +- 2sqrt( 43 ))/2 }}} 
{{{h = -1 +- sqrt( 43 ) }}}
Only the positive result makes sense in this problem.
{{{highlight(h=-1+sqrt(43))}}}
Then,
{{{b=-2+2sqrt(43)+4}}}
{{{highlight(b=2+2sqrt(43))}}}