jawab...tolong ya...MATEMATIKA

1) 6x + 9y - 7z - 10
Koefisien Z= -7 Jawaban: C

2) 6x-8y+5
x= -2 y= -1
6(-2)-8(-1)+5
= -12+8+5= 1 Jawaban: C

3) 3x²+4x-2xy-2x²-x+2xy
= 3x²-2x²+4x-x-2xy+2xy
=x²+3x. Jawaban: A

4) x= a-b+c y=2a+b-c
2x-3y
=2(a-b+c)-3(2a+b-c)
=2a-2b+2c-6a-3b+3c
=2a-6a-2b-3b+2c+3c
= -4a-5b+5c
Jawaban: D