Question

Rezolvati prin metoda substitutiei sistemele :
a ) x + 4y + 2 = 0
    2x-4y+1 = 0
b) 3x + y - 7 = 0
   - 3x + 4y = -2
c) 3a + b - 8 =0
   a + 2b + 6 = 0
d) 0,6x -y + 0,6=0
   x+ 7y + 2 = 0

Answer 1

a)
x=-4y-2
2(-4y-2)-4y+1=0
-8y-4-4y+1=0
-12y=3
y=-1/4
x=1-2=-1
b)3x=-y+7
-(-y+7)+4y=-2
y-7+4y=-2
5y=5
y=1
x=-1+7=6
c)
a=-2b-6
3(-2b-6)+b-8=0
-6b-18+b-8=0
-5b-26=0
b=-26/5
a=2.26/5-6=(52-30)/5=22/5

d)3x/5-y+3/5=0
x+7y+2=0
x=-7y-2
3(-7y-2)/5-y+3/5=0
-21y-6-5y+3=0
-26y=3
y=-3/26

x=7.3/26-2=(-21-52)/26=-73/26