Question 1071189
The arch meets with the ground are the values of
{{{ x }}} where {{{ y = 0 }}}
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{{{ y = -.9*( x + 3 )*( x - 3 ) }}}
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{{{ x = -3 }}}
{{{ y = -.9*( -3 + 3 )*( -3 - 3 ) }}}
{{{ y = -.9*0*( -6 ) }}}
{{{ y = 0 }}}
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{{{ x = 3 }}}
{{{ y = -.9*( 3 + 3 )*( 3 - 3 ) }}}
{{{ y = -.9*6*0 }}}
{{{ y = 0 }}}
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The distance between ( -3, 0 ) and ( 3, 0 )
is {{{ 3 -(-3) = 6 }}}
The width of the arch at ground level is 6 ft
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Here's the plot of the equation:
{{{ graph( 400, 400, -4, 4, -1, 10, -.9*( x + 3 )*( x - 3 )  ) }}}