Question

Алгебра 7клас даю 10балов​

Answer 1

$1)7ab+21a-7b-21=(7ab-7b)+(21a-21)=7b(a-1)+21(a-1)=\\\\=(a-1)(7b+21)=7(a-1)(a+3)$

$2)6mn+60-30m-12n=(6mn-12n)+(60-30m)=6n(m-2)+30(2-m)=\\\\=6n(m-2)-30(m-2)=(m-2)(6n-30)=6(m-2)(n-5)$

$3)-abc-3ac-4ab-12a=(-abc-3ac)-(4ab+12a)=\\\\=-ac(b+3)-4a(b+3)=(b+3)(-ac-4a)=-a(b+3)(c+4)$

$4)a^3-ab-a^2b+a^2=(a^3-a^2b)+(a^2-ab)=a^2(a-b)+a(a-b)=\\\\=(a-b)(a^2+a)=a(a-b)(a+1)$