[tex]\displaystyle\bf\\a^2+2a-35=0\\\\a^2\underbrace{-5a+5a}+2a-35=0\\\\a^2-5a+7a-35=0\\\\a(a-5)+7(a-5)=0\\\\(a-5)(a+7)=0\\\\\implies~~a-5=0~~or~~a + 7=0\\\\a-5=0~~\implies~~\boxed{\bf a_1=5}\\ \\a+7=0~~\implies~~\boxed{\bf a_2=-7}[/tex]
