`1)36a^2-49b^2=(6a)^2-(7b)^2=(6a-7b)(6a+7b)`
`2)196a^2-4b^2=(14a)^2-(2b)^2=(14a-2b)(14a+2b)`
`3)25a^2-49b^4=(5a)^2-(7b^2)^2=(5a-7b^2)(5a+7b^2)`
`4)1/4a^2-1/9b^2=(1/2a)^2-(1/3b)^2=(1/2a-1/3b)(1/2a+1/3b)`
`5)4/9a^4-25/4=(2/3a^2)^2-(5/2)^2=(2/3a^2-5/2)(2/3a^2+5/2)`
`6)25a^2-1/4b^2=(5a)^2-(1/2b)^2=(5a-1/2b)(5a+1/2b)`
`7)1/25-36x^2=(1/5)^2-(6x)^2=(1/5-6x)(1/5+6x)`
`8)(a-b)^2-c^2=(a-b-c)(a-b+c)`
`9)(a+b)^2-4=(a+b)^2-2^2=(a+b-2)(a+b+2)`
`10)(a-2b)^2-4b^2=(a-2b)^2-(2b)^2=(a-2b-2b)(a-2b+2b)=(a-4b)a`
Hằng đẳng thức: `a^2-b^2=(a-b)(a+b)`