1)x²+y²=74
x+y=12 ⇒x=12-y;⇒ (12-y)²+y²=74 ⇒144-24y+y²+y²=74 ⇒
2y²-24y-70=0 ⇒y₁=((24+√(576+4·2·70))/4=((24+√1136)/4=(24+33.7)/4=14.425;
y₂=(24-33.7)/4=-2.425;⇒x₁=12-14.425=-2.425;x₂=12+2.425=14.425;
2)x²-y²=32
x-y=4 x=4+y;⇒(4+y)²-y²=32;⇒16+8y+y²-y²=32 ⇒8y=16;y=2;x=4+2=6;