Rozwiąż układ równań metoda: podstawiania , przeciwnych współczynników zadania:
a)6x-2y=9
3x+y-4,5=0
b)0,1x-0,2y=0,7
-2x+4y=-14
c)4a-7b=-19
3a+2b=22
d)5(x-3y)=-7(3y-x)
-3(x+4)+2(3-5y=0
e)2x+5y+3z=-1
0,5x-y=2-0,7z
11(x-y)=12+z
f)2y+1=-z-2/3x
2x+3y-z=4
3x+2y+z=1/4
g)a+b+c+d=10
a-b+c-d=-2
a+b+c-d=2
h)2x-y=-7
4(x+1)+2y=18
i)6x-2y=10
3x+4(1-y)=36
j)2y=1/3(x-1)+7
1-x=4(y-1)
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a)6x-2y=9
3x+y-4,5=0
{-2y=9-6x
{3x+y=4,5
{y=-4,5+3x
{3x+y=4,5
{y=-4,5+3x
{3x -4,5+3x=4,5
{y=-4,5+3x
{6x=9
{y=-4,5+3x
{x=9/6
{y=-4,5+3x
{x= 1,5
y=-4,5+3*1,5=-4,5+4,5=0
x=1,5 y=0
b)0,1x-0,2y=0,7 /*10
-2x+4y=-14 /:2
x-2y=7 stąd x=7+2y
(-2)*(7+2y)+4y=-14
-14-4y+4y=14
0=0 równanie tożsamościowe - ma nieskończenie wiele rozwiązań
c)4a-7b=-19
3a+2b=22
{4a-7b=-19 stąd a=(7y-19)/4
{-2a+4b=-14 /*2
{4a-7b=-19
{-4a+8b=-28
{b=-47
{a=[7*(-47)-19]:4=(-329-19):4=(-348):4=-87
d)5(x-3y)=-7(3y-x)
-3(x+4)+2(3-5y=0
{5(x-3y)=-7(3y-x)
{-3(x+4)+2(3-5y)=0
{5x-15y=-21y+7x /+21y-7x
{-3x-12+6-10y=0 /+6
{-2x+6y=0 /:(-2)
{-3x+10y=6
x-3y=0 stąd x=3y
-3*3y+10y=6
-9y+10y=6
y=6
x=3*6=18
e)2x+5y+3z=-1
0,5x-y=2-0,7z
11(x-y)=12+z
{ 2x + 5y + 3z = - 1
{ 0,5x - y = 2 - 0,7z
{ 11(x - y) = 12 + z
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 11[x - (0,5x + 0,7z - 2)] = 12 + z
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 11(x - 0,5x - 0,7z + 2) = 12 + z
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 11x - 5,5x - 7,7z + 22 = 12 + z
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 5,5x - 8,7z = - 10
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 5,5x = 8,7z - 10 /*10
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ 55x = 87z - 100 /:55
{ 2x + 5y + 3z = - 1
{ y = 0,5x + 0,7z - 2
{ x = 87/55z - 100/55
{ x = 87/55z - 100/55
{ y = 0,5( 87/55z - 100/55) + 0,7z - 2
{ 2x + 5y + 3z = - 1
{ x = 87/55z - 100/55
{ y = 87/110z - 100/110 + 0,7z - 2
{ 2x + 5y + 3z = - 1
{ x = 87/55z - 100/55
{ y = 87/110z - 100/110 + 77/110z - 222/110
{ 2x + 5y + 3z = - 1
{ x = 87/55z - 100/55
{ y = 164/110z - 322/110
{ 2x + 5y + 3z = - 1
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 2x + 5y + 3z = - 1
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 2(87/55z - 100/55) + 5(82/55z - 161/55) + 3z = - 1
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 174/55z - 200/55 + 410/55z - 805/55 + 3z = - 1
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 584/55z - 1005/55 + 165/55z = - 55/55
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 749/55z = 950/55 / *55
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ 749z = 950 / : 749
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ z = 950/749
{ x = 87/55z - 100/55
{ y = 82/55z - 161/55
{ z = 1,3
{ x = 1,6z - 1,8
{ y = 1,5z - 2,9
{ z = 1,3
{ x = 1,6*1,3 - 1,8
{ y = 1,5*1,3 - 2,9
{ z = 1,3
{ x = 2,1 - 1,8
{ y = 1,2 - 2,9
{ z = 1,3
{ x = 0,3
{ y = - 1,7
{ z = 1,3
f)2y+1=-z-2/3x
2x+3y-z=4
3x+2y+z=1/4
g)a+b+c+d=10
a-b+c-d=-2
a+b+c-d=2
{ 2a + 2c = 8 / :2
{ a + b + c + d = 10
{ 2a - 2d = - 6 /:2
{ a + b + c - d = 2
{ a + c = 4
{ a - d = - 3
{ a + b + c + d = 10
{ a + b + c - d = 2
{ a + c = 4
{ a - d = - 3
{ 4 + b + d = 10
{ 4 + b - d = 2
{ a + c = 4
{ a - d = - 3
{ b + d = 6
{ b - d = - 2
{ a + c = 4
{ a - d = - 3
{ 2b = 4 /:2
{ d = b + 2
{ a + c = 4
{ a - d = - 3
{ b = 2
{ d = 4
{ a = d - 3
{ b = 2
{ c = 4 - a
{ d = 4
{ a = 1
{ b = 2
{ c = 3
{ d = 4
h)2x-y=-7
4(x+1)+2y=18
{2x - y= -7
{4x +4 + 2y= 18
{2x-y= -7 /* (-2)
{4x + 2y = 14
{-4x +2y = 14
{4x +2y = 14
{-4x + 2y + 4x + 2y= 14+14
{4y= 28 /:4
y= 7
2x -y= -7
2x -7 = -7
2x = -7+7
2x =0 /:2
x= 0
i) 6x - 2y = 10
3x + 4 - 4y = 36
{6x - 2y = 10
{3x - 4y = 36 - 4
{6x - 2y = 10
{3x - 4y = 32 *(-2) 3x - 4* -9 = 32
{6x - 2y = 10 3x = 32 - 36
{-6x + 8y = -64 3x = - 4 / 3
+_______________ x = -0,75
6y = - 54 /6
y = -9
x = - 0,75
y = -9
j)
2y=1/3(x-1)+7/*31-x=4(y-1)
6y=x-1+21
1-x=4y-4
6y-x=20
-x-4y=-5/*(-1)
-x+6y=20
x+4y=5
10y=25
x+4y=5
y-2,5
x=5-10
y=2,5
x=-5