Question

Tentukan himpunan penyelesaian dari persamaan berikut ini dengan metode substitusi.
a. 2x = -3y - 14
-4y = -3x + 30

b. 2x = -5y + 20
3x + 4y = 23

c. 4x - 2y - 12 = 0
2x = -3y + 14

d. 3x - 5y = -13
7x + 10y = 13

Answer 1

A. 2x+ 3y=14 ...1
    3x - 4y=30 ....2
    x= {(3.30).(14.-4)} / {(3.3).(2.-4)} = 5040/72 = 70
    subtitusikan x=70
    2.(70) + 3y=14 
    140+3y=14
    y=140-14 = 126/3 = 42

    hp= {x=70 y=42}

B. 2x + 5y = 20 ...1
    3x + 4y = 23 ....2
   x={(5.23).(20.4)} / (5.3)(2.4) = 9200/120 = 76,6
   x=76,6
   2.(76,6) + 5y = 20
   153,2 +5y = 20
   y=153,2-20 = 133,3/5 = 26,46 

   hp= {x=76,6. y=26,46}
 
C. 4x - 2y = 12 ......1
    2x + 3y = 14 ..... 2
    x= -2.14 x 12.3 / -2.2 x 4.3 = -864 / -48 = 18
    x=18
    4.(18) - 2y = 12
    72 - 2y = 12
    y= 72-12 = 60/2 = 30

   hp = {x=18,y=30}

D. 3x - 5y = -13
    7x + 10y = 13
    x= -13.10 x -5,13 / -5.7 x 3.10 = 8450 / -1050 = -8
    x=- 8
    3.-8 - 5y = -13
    -32 - 5y = 13
    y= 32+13 = 45/5 = 9

   hp= {x=-8 y=9}