Question

va rog frumos pe lung dau 50 de puncte va rog frumos dau coroana
Reyolvati in R x Rprin metoda substitutiei sistemul de ecuatii.
a)acolada y=-5x+1
4+y=0

b)acolada x+y=7
4x-y=3

c)acolada y-2x=1
6x-y=7

d)acolada x+4y+2=0
2x-4y+1=0

e)acolada 2x-3y=-1
x+y=2

f)acolada x-y=1
2x+y=5

Answer 1

a)acolada y=-5x+1
4+y=0 => y=-4

-4=-5x+1
-4-1=-5x
-5=-5x
x=1


b)acolada x+y=7 => x=7-y
4x-y=3
4(7-y)-y=3
28-4y-y=3
-5y=3-28
-5y=-25
y=-5
x=7-(-5)
x=7+5
x=12

c)acolada y-2x=1 => y=1+2x
6x-y=7
6x-1+2x=7
8x=7+1
8x=8
x=1

y=1+2x
y=1+2
y=3

d)acolada x+4y+2=0
2x-4y+1=0

acolada  x+4y=-2 => x=-2-4y
2x-4y=-1
2(-2-4y)-4y=-1
-4-8y-4y=-1
-12y=-1+4
-12y=3
y=-4

x=-2-4y
x=-2-(-4)*4
x=-2-(-16)
x=-2+16
x=14

e)acolada 2x-3y=-1
x+y=2 => x=2-y

2(2-y)-3y=-1
4-2y-3y=-1
4-5y=-1
-5y=-1-4
-5y=-5
y=1
x=2-y
x=2-1
x=1

f)acolada x-y=1 => x=1+y
2x+y=5
2(1+y)+y=5
2+2y+y=5
3y=5-2
3y=3
y=1
x=1+1
x=2