a){4a-2=b
{3a+7b=1,5
b=-4a+2
3a+7(-4a+2)=1,5
b=-4a+2
3a-28a+14=1,5
b=-4a+2
-25a=1,5-14
b=-4a+2
25a=-12,5/"(-25)
b=-4a+2
a=0,5
b=4*0,5+2
a=0,5
b=4
a=0,5
b){5x=4-2y
{4x+y=3
5x=4-2y
y=3-4x
5x=4-2(3-4x)
y=3-4x
5x=4-6+8x
y=3-4x
-3x=-2/:(-3)
y=3-4x
x= 2/3
y=3-4x
x= 2/3
y=3-4* 2/3
x= 2/3
y=3/3 - 8/3
x= 2/3
y=-1 i 2/3
c){6x-3y=9
{x+5y=-9.5
6x-3y=9
x= -9,5-5y
6(-9,5-5y)- 3y=9
x= -9,5-5y
-57-30y-3y=9
x= -9,5-5y
-33y=66 /:(-33)
x= -9,5-5y
y=-2
x=-9,5-5 *(-2)
y=-2
x=0,5
