tolong dijawab ya. makasih

nomor 2 jawabannya-3
nomor 3 jawabannya e

nomor 2:

4x -3y = -8

5x +2y =13

--------------  -

-x -5y = -21

Atau bisa dijadikan positif jadi

X + 5y = 21

 

(a-2, a+1)  *(jadi x= a-2, y=a+1) substitusikan ke persamaan diatas

a-2 + 5(a+1) = 21

a-2 + 5a +5 = 21

6a +3 = 21

6a= 21-3

a = 18/6 = 3

Jawaban : D

 

nomor 3:

4y+3z=72 | x 2 | 8y + 6 z = 144      …(3)

5x+2z=66 | x 3 | 15x+6z = 198       …(2)

                             ---------------------------- -

                             8y-15x = 144 – 198

               8y -15 x = -54     … (4)

 

8y -15 x = -54 | x 3 | 24y -45 x = -162    … (4)

4x + 3y  =76   | x 8 | 32x + 24y = 608      …..(1)

                                   ------------------------- -

                                   -45x -32x = -162 -608

                                    -77 x = -770

                                        X = -770/-77 = 10

4x+3y = 76

4 . 10 + 3y= 76

3y = 76 – 40

Y = 36/3 = 12

 

5x +2z = 66

5 . 10 +2z=66

2z = 66-50

Z = 16 /2 = 8

 

Jadi x = 10 , y = 12 , dan z = 8

(10,12,8)

Jawaban : A