Verified answer

Объяснение:

1.

1) 7m³-21mn-45mn+15n²-4m²32mn

2) a³+3a²b-6ab²-4a²b-12ab²+24b³

3) -5c²(12c²+42c-8c³-28c²)= -60c⁴-210c³+40c⁵+140c⁴

4) 9m²+15mn-12mn-20n²-(9m²+18mn-2mn-4n²)=9m²+15mn-12mn-20n²-9m²-18mn+2mn+4n²

2.

1) x²-3x+6x+18-(x²+9x+3x+27)=x²-3x+6x+18-x²-9x-3x-27=9

2) 6(7х-3)=9(4х+3)

42х-18=36х+18

6х=х-2

5х=-2

х= -2/5