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Đáp án+Giải thích các bước giải:

`a)`

`(2a-b)(b+4a)+2a(b-3a)`

`=2ab+8a^2-b^2-4ab+2ab-6a^2`

`=(8a^2-6a^2)-b^2+(2ab-4ab+2ab)`

`=2a^2-b^2`

`b)`

`(3a-2b)(2a-3b)-6a(a-b)`

`=6a^2-9ab-4ab+6b^2-6a^2+6ab`

`=(6a^2-6a^2)+6b^2+(-9ab-4ab+6ab)`

`=6b^2-7ab`

`c)`

`5b(2x-b)-(8b-x)(2x-b)`

`=10bx-5b^2-(16bx-8b^2-2x^2+bx)`

`=10bx-5b^2-16bx+8b^2+2x^2-bx`

`=(-5b^2+8b^2)+2x^2+(10bx-16bx-bx)`

`=3b^2+2x^2-7bx`

`d`

`2x(a+15x)+(x-6a)(5a+2x)`

`=2ax+30x^2+5ax+2x^2-30a^2-12ax`

`=(30x^2+2x^2)-30a^2+(2ax+5ax-12ax)`

`=32x^2-30a^2-5ax`

`#ld`