有幾條數學唔識...

1.(15a-14c^2)^2
=(15a)^2-2*15a*14c^2+(14c^2)^2
=225a^2-420ac^2+196c^4

2.(3a^2+4b)^2
=(3a^2)^2+2*3a^2*4b+(4b)^2
=9a^4+24a^2b+14b^2

3.(10^2-3^2)
=100-9
=91

另解(10^2-3^2)
=(10+3)(10-3)
=13*7
=91
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因識分解
1.225b^2-196c^2
=(15b)^2-(14c)^2
=(15b+14c)(15b-14c)

2.25a^2+30ab+9b^2
=(5a)^2+2*5a*3b+(3b)^2
=(5a+3b)^2

3.100x^2+180xy+81y^2
=(10x)^2+2*10x*9y+(9y)^2
=(10x+9y)^2

4.64a^2-96ab+36b^2
=(8a)^2-2*8a*6b+(6b)^2
=(8a-6b)^2

5.121-225b^2
=11^2-(15b)^2
=(11+15b)(11-15b)

6.81c^2-108cd+36d^2
=(9c)^2-2*9c*6d+(6d)^2
=(9c-6d)^2

Ok!

1.(15a-14c^2)^2=225a^2-196c^4
2.(3a^2+4b)^2=9a^2+16b^2
3.(10^2-3^2)=91
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因識分解
1.225^2-169^2=22064
2.25a^2+30ab+9b^2=(5a+3)^2
3.100x^2+180xy+81y^2=(10x+9)^2
4.64a^2-96ab+36b^2=4(4a-3)^2
5.121-225b^2=(11+15b)(11-15b)
6.81c^2-108cd+36d^2=9(3c-2)^2

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