3. Tentukan hasil pengurangan bentuk aljabar berikut a. (42n+35m+7) - (-50m-20n+9) b. (5x+3) - (x-1) c. (2y+15z) - (4y-8)

a. (42n+35m+7) - (-50m-20n+9)
    = 42n+35m+7 +50m+20n-9
    = 42n+20n +35m+50m +7-9
    = 62n + 85m - 2

 b. (5x+3) - (x-1)
    = 5x+3 -x+1
    = 4x + 4

c. (2y+15z) - (4y-8)
    = 2y+15z -4y+8
    = -2y + 15z + 8

a. (42n+35m+7) - (-50m-20n+9)
=42n+35m+7 +50m+20n-9
=35m+50m+42n+20n+7-9
=85m+62n-2

b. (5x+3) - (x-1)
=5x+3-x+1
=5x-x+3+1
=4x+4

c. (2y+15z) - (4y-8)
=2y+15z-4y+8
=2y-4y+15z+8
= -2y+15z+8

gak tau bener apa gak. soalnya caranya aku lupa2 inget ehehe...
maaf klo salah..