Question

Cara mengerjakannya gmn?

Answer 1

X+y = 4 --> x = 4 - y 
sub ke x² - 2x + y² + 4y = 20

(4 -y)² - 2( 4- y) + y² + 4y = 20
16 -8y +y² -8 + 2y + y² +4y = 20
2y² - 2y - 12= 0
y² - y - 6= 0 --> (y-3)(y+2)= 0
y = 3 --> x = 4- y = 1 --> (1,3)
y  = - 2--> x = 4 -y = 6 --> (6,-2)