Question

Yang pakar mtk tolong bantu ya (y) no 15,18,19,20 sama 21

Answer 1

15)
3x + y = -10 |2|
2x + 3y = -16 |3|
--------------
6x + 2y = -20
6x + 9y = -48
------------- -
-7y = -28
y = 4

3x + (-4) = -10
3x = -10 + 4
3x = -6
x = -2

3(-2) - 2(-4)
-6 + 8 = 2

19)
y - y1 / y2 - y1 = x - x1 / x2 - x1
y - 0 / 3 - 0 = x + 6 / 3 + 6
y - 0 / 3 = x + 6 / 9
9y - 9 = 3x + 18
------------- : 9
y = 1/3x + 2

20)
y - y1 / y2 - y1 = x - x1 / x2 - x1
a - 3 / -3 - 3 = 4 + 2 / 1 + 2
a - 3 / - 6 = 6 / 3
3a - 9 = -36
3a = -36 + 9
3a = -27
a = 9

Answer 2

15) 3x+y=-10 (x3)
2x+3y=-16 (x1)
9x+3y=-30
2x+3y=-16
----------------- -
7x = -14
x = -14/7 = -2

3x+y=-10
3.-2 + y=-10
-6 + y=-10
y= -10+6= -4

jadi, 3x-2y:
3.(-2) - 2.(-4)
= -6 + 8
= 2