ini bantuin lagi yaa pliss

misal
mangga = x
apel = y
2x + y = 15.000 |×2
x + 2y = 18.000
maka
4x + 2y = 30.000
x + 2y = 18.000
--------------------------(-)
3x = 12.000
x = 4.000
disubtitusi ke pers :
x + 2y = 18.000
4.000 + 2y = 18.000
2y = 18.000 - 4.000
2y = 14.000
y = 7.000
harga 5x + 3y
= 5(4.000) + 3(7.000)
= 20.000 + 21.000
= 41.000
harga 5kg mangga & 3kg apel = 41.000

x + 3y = 5 |×2
2x + 9y = - 20
maka
2x + 6y = 10
2x + 9y = - 20
---------------------(-)
- 3y = 30
y = - 10
disubtitusi ke pers :
x + 3y = 5
x + 3(-10) = 5
x - 30 = 5
x = 5 + 30
x = 35
hp = ( 35 , - 10 )

4x + 5y = 17
2x + 3y = 11 |×2
maka
4x + 5y = 17
4x + 6y = 22
--------------------(-)
- y = - 5
y = 5
disubtitusi ke pers
2x + 3y = 11
2x + 3(5) = 11
2x + 15 = 11
2x = 11 - 15
2x = 4
x = 2
hp = ( 2 , 5 )

x² - 3x + 2 = 0
x1 + x2 = - b / a
x1 + x2 = 3/1
x1 + x2 = 3

x² - x - 6 = 0
A • B = c/a
A • B = - 6/1
A • B = - 6

2x² - 4px + 8 = 0
A + B = 10
- b / a = 10
4p / 2 = 10
4p = 10 × 2
4p = 20
p = 5

2kx² - 9x + k² = 0
X1 • X2 = 10
c/a = 10
k² / 2k = 10
k² = 2k • 10
k² = 20k
k² - 20k = 0
k ( k - 20) = 0
k = 0 atau k = 20
yg memenuhi k = 20