посчитайте способом подстановки систему уравнений: г)

это немаё решение

begin{gathered}80a) left{begin{array}{l}x+y=2x^2-y^2=100end{array}right left{begin{array}{l}x+y=2(x-y)(x+y)=100end{array}right left{begin{array}{l}x+y=2(x-y)cdot 2=100end{array}right\left{begin{array}{l}x+y=2x-y=50end{array}right oplus ominus left{begin{array}{l}2x=522y=-48end{array}right left{begin{array}{l}x=26y=-24end{array}right Otvet: (26;-24) .end{gathered}

begin{gathered}b) left{begin{array}{l}x+y=-5x^2-y^2=5end{array}right left{begin{array}{l}x+y=-5(x-y)(x+y)=5end{array}right left{begin{array}{l}x+y=5-5, (x-y)=5end{array}right\left{begin{array}{l}x+y=-5x-y=-1end{array}right oplus ominus left{begin{array}{l}2x=-62y=-4end{array}right left{begin{array}{l}x=-3y=-2end{array}right Otvet: (-3;-2) .end{gathered}

begin{gathered}c) left{begin{array}{l}y-3x=0x^2+y^2=40end{array}right left{begin{array}{l}y=3xx^2+(3x)^2=40end{array}right left{begin{array}{l}y=3x10x^2=40end{array}right\left{begin{array}{l}y=3xx^2=4end{array}righty left{begin{array}{l}y=3xx=pm 2end{array}rightend{gathered}

begin{gathered}1. left{begin{array}{l}y=3xx=-2end{array}right left{begin{array}{l}y=-6x=-2end{array}right\2. left{begin{array}{l}y=3xx=2end{array}right left{begin{array}{l}y=6x=2end{array}right\ ext{O}tvet: (-2;-6) , (2;6) .end{gathered}

begin{gathered}d) left{begin{array}{l}2x+y=0xy=2end{array}right left{begin{array}{l}y=-2xx(-2x)=2end{array}right left{begin{array}{l}y=-2x-2x^2=2end{array}right left{begin{array}{l}y=-2xx^2=-1end{array}right\ ext{O}tvet: varnothing , tak kak x^2geq 0 i x^2ne -1 .end{gathered}