问一下有关分解因数的几道数学题

都是直接套公式的

1. 0.49a^2-144b^2
=(0.7a+12b)(0.7a-12b)

2. 25/4a^2-x^2y^2
=(5/2a+xy)(5/2a-xy)

3. (m+n)^2-n^2
=(m+n+n)(m+n-n)
=m(m+2n)

4. 169(a-b)^2-196(a+b)^2
=[13(a-b)+14(a+b)][13(a-b)-14(a+b)]
=(27a+b)(-a-27b)
=-(27a+b)(a+27b)

5. b^2-22b+121
=(b-11)^2

6. y^2+y+1/4
=(y+1/2)^2

1.(0.7a+12b)(0.7a-12b)
2.(5a/2 + xy )(5a/2 - xy)
3.m(m+2n)
4.(27b+a)(b-27a)
5.(b-11)^2
6.(y+ 1/2)^2
完了.

1. 0.49a^2-144b^2
=(0.7a-12b)(0.7a+12b)

2. 25/4a^2-x^2y^2
=(5a/2+xy)(5a/2-xy)

3. (m+n)^2-n^2
=(m+n+n)(m+n-n)
=m(m+2n)

4. 169(a-b)^2-196(a+b)^2
=[13(a-b)+14(a+b)][13(a-b)-14(a+b)]
=(27a+b)(-a-27b)
=-(27a+b)(a+27b)

5. b^2-22b+121
=(b-11)^2

6. y^2+y+1/4
=1/4(4y^2+4y+1)
=1/4(2y+1)^2