tolong di jawab gan secepat nya

1. 7x-4y+6-4x+y-6 = 7x-4x-4y+y+6-6 = 3x-3y

2. -6ab(4ab²+2a²b-3ab) = -24a²b³-12a³b²+18a²b²

3. (2x+3y)(x-4y) = 2x²-8xy+3xy-12y= 2x²-5xy-12y

4. (a-4b)(a²+4ab+16b²) = a³+4a²b+16ab²-4a²b-16ab²-64b³= a³+4a²b-4a²b+16ab²-16ab²-64b³= a³-64b³