Question 1027656
Plot monthly charges, {{{ C }}}, in cents,  on the vertical axis
Plot number of kilowatt hours used per month, {{{ x }}}
on the horizontal axis
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{{{ 11.5 }}} cents / kWh is the slope of the line
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( 380, 5165 ) is given as a point on the line
( note that I converted the cost to cents )
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Use the general point-slope formula
{{{ ( C - 5165 ) / ( x - 380 ) = 11.5 }}}
{{{ C - 5165 = 11.5*( x - 380 ) }}}
{{{ C = 11.5x + 5165 - 11.5*380 }}}
{{{ C = 11.5x + 5165 - 4370 }}}
{{{ C = 11.5x + 795 }}}
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check the answer:
( 380, 5165 )
{{{ C = 11.5x + 795 }}}
{{{ 5165 = 11.5*380 + 795 }}}
{{{ 5165 = 4370 + 795 }}}
{{{ 5165 = 5165 }}}
OK
( note that if no electricity is used, you still pay $7.95/month )