Factor 7a^3+28a^2-35a
\(7a^3+28a^2-35a=7a(a^2+4a-5)=(*)\\ \\-------------------------------\\ \\a^2+4a-5-a^2-a+5a-5=a(a-1)+5(a-1)=(a-1)(a+5)\\ \\-------------------------------\\ \\(*)=7a(a-1)(a+5)\)
\(7a^3+28a^2-35a =\\ \\=7a(a^2+4a+a-a-5) =\\ \\= 7a(a^2+5a -a-5)=\\ \\=7a[(a(a+5)-(a+5))]=\\ \\=7a(a+5)(a-1)\)
