tolong yang jago matematika bagian c,d,e.

d.x+y=7
y=x-4
jawaban:
x+y=7 diubah kepersamaan y=7-x
y=y
7-x=x-4
-x-x=-4-7
-2x=-11
x=-11/2

C)
7y + 5x = 6
x = 0
7y + 5(0) = 6
7y = 6
y = 6/7

(x, y) → (0, 7/6)

y = 0
7(0) + 5x = 6
5x = 6
x = 6/5

(x, y) → (0, 6/5)

y = 2x + 9
x = 0
y = 2(0) + 9
y = 9

(x, y) → (0, 9)

y = 0
0 = 2x + 9
2x = -9
x = -9/2

(x, y) → (-9/2, 0)

d)
x + y = 7
x = 0
0 + y = 7
y = 7

(x, y) → (0, 7)

y = 0
x + 0 = 7
x = 7

(x, y) → (7, 0)

y = x - 4
x = 0
y = 0 - 4
y = -4

(x, y) → (0, -4)

y = 0
0 = x - 4
x = 4

(x, y) → (4, 0)

e)
7x = 3y + 11
x = 0
7(0) = 3y + 11
0 = 3y + 11
3y = -11
y = -11/3

(x, y) → (0, -11/3)

y = 0
7x = 3(0) + 11
7x = 11
x = 11/7

(x, y) → (11/7, 0)

3y = x - 7
x = 0

3y = 0 - 7
3y = -7
y = -7/3

(x, y) → (0, -7/3)

y = 0
3y = x - 7
3(0) = x - 7
0 = x - 7
x = 7

(x, y) → (7, 0)