Tolong bantu Abang kk​

Penjelasan dengan langkah-langkah:

3.7x + 2y = 19 (.4)

4x – 3y = 15 (.7)

28x + 8y = 76

28x – 21y = 105

__________ –

29y = -29

y = -29/29

y = -1

Substitusikan ke salah satu persamaan :

28x + 8y = 76

28x + 8(-1) = 76

28x – 8 = 76

28x = 76 + 8

28x = 84

x = 84/28

x = 3

Nilai dari 4x + 2y

= 4(3) + 2(-1)

= 12 + (-2)

= 12 – 2

= 10

4.Buku tulis = x

Pulpen = y

a.2x + 3y = Rp.10.200,-

3x + 4y = Rp.14.400,-

b.2x + 3y = Rp.10.200,- (.4)

3x + 4y = Rp.14.400,- (.3)

8x + 12y = Rp.40.800,-

9x + 12y = Rp.43.200,-

_________________ –

-1x = – Rp.2.400,-

x = – Rp.2.400,-/-1

x = Rp.2.400,-

Substitusi :

9x + 12y = Rp.43.200,-

9(Rp.2.400,-) + 12y = Rp.43.200,-

Rp.21.600,- + 12y = Rp.43.200,-

12y = Rp.43.200,- – Rp.21.600,-

12y = Rp.21.600,-

y = Rp.21.600,-/12

y = Rp.1.800,-

Harga tiga buku tulis dan empat Pulpen :

3x + 4y

= 3(Rp.2.400,-) + 4(Rp.1.800,-)

= Rp.7.200,- + Rp.7.200,-

= Rp.14.400,-

5.2x + 4y = -9

-4y = 2x + 9

-2y = x + 9

jadi m = 1/-2

maka persamaan garis yang sejajar -2y = x + 9

y – y1 = m(x – x1)

y – 4 = -1/2 (x – (-3))

y – 4 = -1/2 (x + 3)

y – 4 = -1/2 (x + 9/3)

y – 4 = -1/2x – 9/6

y – 4 = -1/2x – 3/2

y = -1/2x – 3/2 + 4

y = -1/2x – 3/2 + 8/2

y = -1/2x + 5/2