Bài 1 :
`1,a²-4b²=(a-2b)(a+2b)`
`2,4x²-9y²=(2x-3y)(2x+3y)`
`3,25a^4-1=(5a²-1)(5a²+1)`
`4,a^4-81=(a²-9)(a²+9)=(a-3)(a+3)(a²+9)`
`5,121-36x²=(11-6x)(11+6x)`
`6,144a²-81=(12a-9)(12a+9)`
`7,36a²-49b²=(6a-7b)(6a+7b)`
`8,a^4-4b²=(a²-2b)(a²+2b)`
`9,1/4a²-b²=(1/2a-b)(1/2a+b)`
`10,4/9a^4-25/4=(2/3a²-5/2)(2/3a²+5/2)`
`11,a^4-16b^4=(a²-4b²)(a²+4b²)=(a-2b)(a+2b)(a²+4b²)`
`12,(a-b)²-c²=(a-b-c)(a-b+c)`
`13,(a-2b)²-4b²=(a-2b-2b)(a-2b+2b)=(a-4b).a`
`14,(a+3b)²-9b²=(a+3b-3b)(a+3b+3b)=a(a+6b)`
`15,(a-5b)²-16b²=(a-5b+4b)(a-5b-4b)=(a-b)(a-9b)`
`16,36a²-(3a-2b)²=(6a-3a+2b)(6a+3a-2b)=(3a+2b)(9a-2b)`
`17,4a²-(a+b)²=(2a-a-b)(2a+a+b)=(a-b)(3a+b)`
`18,49a²-(2a-b)²=(7a-2a+b)(7a+2a-b)=(5a+b)(9a-b)`
Xin hay nhất !