Question 901290
This is meant to show that: 
" When the supply goes up, the demand goes down "
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Here are the plots of the equations
The supply goes up and Demand goes down
{{{ graph( 600, 600, -10, 60, -40, 230, 4x + 5, -2x + 81 ) }}}
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(1) {{{ p = 4q + 5 }}}
(2) {{{ p = -2q + 81}}}
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(a)
{{{ q = 53 }}}
(1) {{{ p = 4*53 + 5 }}}
(1) {{{ p = 212 + 5 }}}
(1) {{{ p = 217 }}}
and
(2) {{{ p = -2*53 + 81}}}
(2) {{{ p = -106 + 81 }}}
(2) {{{ p = -25 }}}
217 units are supplied and
-25 units are demanded
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(b)
This gives a surplus
(c)
There is way more supply than demand, so
price is likely to go down