Răspuns:
4.a)2x+2y+2-6x+3y+9=12
8x-4y-4+9-3x-3y=3
-4x+5y=12-11
5x-7y=-5+3
-4x+5y=1. x=(5y-1)/4 substituția
5x-7y=-2
5(5y-1)/4-⁴7y=-⁴2
25y-5-28y=-8
-3y=-3
y=1
x=(5y-1)/4=4/4=1solutia:(1;1)
b)√2x+√5y=7 substituția x=(7-√5y)/√2
√5x-√2y=0
√5(7-√5y)/√2-√2y=0
7√5-√5×√5y-√2×√2y=0
-5y-2y=7√5
-7y=7√5
y=-√5. x=(7-√5y)/√2=(7-5)/√2=2√2/2=√2
soluția,:(√2;-√5)
