Question 548133
(1) {{{ 2x + 4y = 8 }}}
(2) {{{ -2x + y = 12 }}}
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Divide both sides of (1) by {{{2}}}
(1) {{{ x + 2y = 4 }}}
(1) {{{ x = -2y + 4 }}}
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Substitute (1) into (2)
(2) {{{ -2*(-2y + 4) + y = 12 }}}
(2) {{{ 4y - 8 + y = 12 }}}
(2) {{{ 5y = 20 }}}
(2) {{{ y = 4 }}}
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And, since
(2) {{{ -2x + 4 = 12 }}}
(2) {{{ -2x = 12 - 4 }}}
(2) {{{ -2x = 8 }}}
(2) {{{ x = -4 }}}
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The solution is ( -4, 4 )
check answer:
(2) {{{ -2x + y = 12 }}}
(2) {{{ -2*(-4) + 4 = 12 }}}
(2) {{{ 8 + 4 = 12 }}}
(20 {{{ 12 = 12 }}}
OK
and
(1) {{{ x + 2y = 4 }}}
(1) {{{ -4 + 2*4 = 4 }}}
(1) {{{ -4 + 8 = 4 }}}
(1) {{{ 4 = 4 }}}
OK