Diketahui (4,2) merupakan himpunan penyelesaian SPLDV: {ax + by= -4} {cx + ay= 22} nilai b-4c= tolong kk jawabannya pakai cara juga biar pahsm

( 4,2 )
x = 4
y = 2
disubtitusi ke masing2 pers
ax + by = - 4
a( 4 ) + b ( 2) = - 4
4a + 2b = - 4 .. pers 1
bx + ay = 22
b ( 4) + a ( 2) = 22
4b + 2a = 22 ... pers 2
pers 1 & 2 dieliminasi
4a + 2b = - 4 |×2
2a + 4b = 22
maka
8a + 4b = - 8
2a + 4b = 22
-------------------(-)
6a = - 30
a = - 5
disubtitusi ke pers :
2a + 4b = 22
2(-5) + 4b = 22
- 10 + 4b = 22
4b = 22 + 10
4b = 32
b = 8
nilai b - 4a = 8 - 4(-5) = 8 + 20 = 28