Odpowiedzi

2009-12-14T20:07:59+01:00
5x-7y=3/*-2
2x-3y=7/*5
----------
-10x + 14y = -6
10x - 15y = 35
-----------------
-y = 29
y=-29
x= -47




4x-5y=5/*-3
6x-7y=9/*2
------------------
-12x + 15y = -15
12x - 14y = 18
-----------------------
y= 3
x = 5



ad 2

a+b=223
a - b = 25
-------------
a = 223 - b
223 - b - b = 25
-----------------
a = 223 - b
-2b = --198
--------------
a= 223 - b
b = 99
---------------
a = 124
b = 99



2009-12-14T20:09:03+01:00
1.
5x-7y=3 /*(-2)
2x-3y=7 /*5

-10x+14y=-6
10x-15y=35
____________
-y=29 /*(-1)
y=-29


y=-29
2x-3*(-29)=7

y=-29
2x=-80 /:2

y=-29
x=-40


_______________________________
4x-5y=5 /*3
6x-7y=9 /*(-2)

12x-15y=15
-12x+14y=-18
____________
-y=-3 /*(-1)
y=3

y=3
4x-5*3=5

y=3
4x=20 /:4

y=3
x=5

____________________________________________________


2x+3y+18=0
3x+5y+29=0

2x+3y=-18 /*3
3x+5y=-29 /*(-2)

6x+9y=-54
-6x-10y=58
__________
-y=4 /*(-1)
y=-4

y=4
2x+3*4=-18

y=4
2x=-30 /:2

y=4
x=-15


zad. 2
x - pierwsza liczba
y - druga liczba

x+y=223
x-y=23

x=223-y
223-y-y=23

x=223-y
-2y=-200 /:(-2)

x=223-y
y=100

x=223-100
y=100

x=123
y=100

Odp. Pierwsza liczba to 123, a druga liczba to 100.
2009-12-14T20:10:52+01:00
5x-7y=3 /×(-2)
2x-3y=7 /×5
-10x+14y=-6
10x-15y=35
-y=29
y=-29
2x=7-87
x=-40

4x-5y=5 /×3
6x-7y=9 /×(-2)
12x-15y=15
-12x+14y=-18
-y=-3
y=3
4x=5+15
x=5

2x+3y+18=0 /×3
3x+5y+29=0 /×(-2)
6x+9y=-54
-6x-10y=58
-y=4
y=-4
2x=-18+12
x=-3

x+y=223
x-y=25
2x=248
x=124
y=223-124
y=99