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Объяснение:

1.

а)

(4а-а²)/(16-а²)=(а(4-а))/((4-а)(4+а))=а/(4+а)

б)

(mn³-m²n)/(mn)=(mn(n²-m))/(mn)=n²-m

в)

(а²+аb)/ab=(a(a+b))/ab=(a+b)/b

2.

a)

5/ab² - 7/a²b=(5a-7b)/a²b²

б)

1 - 4а/(а-b)=(a-b-4a)/(a-b)=(-3a-b)/(a-b)=

= - (3a+b)/(a-b)

в)

5 + b + 4b/(5+b)=(5(5+b)+b(5+b)+4b)/(5+b)=

=(25+5b+5b+b²+4b)/(5+b)=(b²+14b+25)/(5+b)

г)

(х²+6х+9)/х • (х²+7х)/(х+3)=

=((х+3)²)/х • (х(х+7))/(х+3)=(х+3)(х+7)=

=х²+7х+3х+21=х²+10х+21

д)

(2а²+18)/(а²-9) : (3а²+27)/(9-а²)=

=(2(а²+9))/(а²-9) • (9-а²)/(3(а²+9))=

= 2/(-(9-а²)) • (9-а²)/3= -2/3