Tolong yaa caranya gimanaa....

7.
[ lihat gambar ]
7a + 4c = 2 (x3)
5a + 3c = -1 (x4)

21a + 12c = 6
20a + 12c = -4
---------------------- (-)
a = 6 - (-4)
a = 6 + 4
a = 10 ●

7a + 4c = 2
7(10) + 4c = 2
70 + 4c = 2
4c = 2 - 70
4c = -68
c = -68/4
c = -17 ●


7b + 4d = 1 (x3)
5b + 3d = 0 (x4)

21b + 12d = 3
20b + 12d = 0
--------------------- (-)
b = 3 ●

7b + 4d = 1
7(3) + 4d = 1
21 + 4d = 1
4d = 1 - 21
4d = -20
d = -20 / 4
d = -5 ●

→ a + b + c + d :
= 10 + 3 + (-17) + (-5)
= 10 + 3 - 17 - 5
= 13 - 22
= -9

8.
Det A = (x - 1)5 - (x - 2)4
(x - 1)5 - (x - 2)4 = 5
5x - 5 - (4x - 8) = 5
5x - 5 - 4x + 8 = 5
x = 5 + 5 - 8
x = 10 - 8
x = 2