Tolong di bantu y teman-teman.

Kelas 10 Matematika
Bab Matriks

Matriks A
( a  1  2)
( a  1  a)
( 5  6  7)

Matriks A singular, maka

(a . 1 . 7 + 1 . a . 5 + 2 . a . 6) - (5 . 1 . 2 + 6 . a . a + 7 . a . 1) = 0
(7a + 5a + 12a) - (10 + 6a² + 7a) = 0
24a - 10 - 6a² - 7a = 0
6a² - 17a + 10 = 0
(6a - 5) (a - 2) = 0
6a - 5 = 0
6a = 5
a = 5/6

a - 2 = 0
a = 2

Maka, a = 2 atau a = 5/6