Question

Ex 10 Dau coroana si 16 puncte

Answer 1

a)
4x-2y-2=2 sau
4x-2y=4
3x-2y=1 |×(-1)

4x-2y=4
-3x+2y=-1
________
x / = 3

4x-2y=4 |×3
3x-2y=1 |×(-4)

12x-6y=12
-12x+8y=-4
________
/ 2y = 8 => y=4

=>s (3;4)

b)
4x+y=-16 |×3
2x-4-3y=2 sau
2x-3y=6

12x+3y=-48
2x-3y=6
_________
14x / = -42 => x=-3

4x+y=-16
2x-3y=6 |×(-2)

4x+y=-16
-4x+6y=-12
_________
/ 7y=-28 => y=-4

=>s (-3;-4)

c)
3x+12=4y+12 sau 3x-4y=0
2x-4=y+1 sau 2x-y=5 |×(-4)

3x-4y=0
-8x+4y=-20
__________
-5x / = -20 => x=4

3x-4y=0 |×(-2)
2x-y=5 |×3

-6x+8y=0
6x-3y=15
________
/ 5y=15 => y=3

=>s (4;3)
d)
4x+20=3y+15 sau 4x-3y=-5 |×4
3x+21=4y+12 sau 3x-4y=-9 |×(-3)

16x-12y=-20
-9x+12y=27
_________
7x / = 7 => x=1

4x-3y=-5 |×3
3x-4y=-9 |×(-4)

12x-9y=-15
-12x+16y=36
__________
/ 7y = 21 => y=3

=>s (1;3)