Sagot :
Bonsoir
a)
3x=y+14 3y -2x +21 = 0
y = 3x-14 3(3x-14) -2x + 21 = 0
9x - 42 - 2x +21 = 0
7x - 21 = 0
7x = 21
x = 3
y = 3*3 -14
y = -5
b)
2x+5y=3x-2y-59 7x+9y = 3y -5x +78
5y+2y =3x-2x -59 7x+5x = 3y-9y +78
7y = x-59 12x = -6y+78
x = 7y+59 12(7y+59) = -6y+78
84y + 708 = -6y +78
90y = -630
y = -630/90
y = -7
x = (-7*7) + 59
x = -49 +59
x = 10