問數學題~10~

1.5b² +6cd+3bd+10bc----------------------ans:(2b+3d)(b+2c)
= 5b(b+2c)+3d(b+2c)
=(b+2c)(5b+3d) #

2.4ab-6ab² -2+3b----------------------ans:(2ab-1)(2-3b)
=2ab(2-3b)-(2-3b)
=(2-3b)(2ab-1) #

3.-(5a-b)(b-5a)----------------------ans:b²-10ab+25a² (expand)
=(b-5a)^2
=b²-10ab+25a² #

4. (4x² -9y² )-2x-3y----------------------ans:(2x+3y)(2x-3y-1) factorize!!
=(2x+3y)(2x-3y)-(2x+3y)
=(2x+3y)(2x-3y-1) #

5. 9a² -(b² +26b+169)----------------------ans:(3a+b+13) factorize!!
= (3a)^2 -(b+13)^2
= (3a + b + 13)(3a - b - 13)#

6. (2m+5)÷(5+2m)²/(3-n)²X2m+5/3m-mn ----------------------ans: 3-n/m simplify
=(2m+5)x(3-n)²/(5+2m)²x2m+5/m(3-n)
=3-n/m #
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