Đáp án:
1/ 25a²-$\frac{1}{4}$ b²
=(5a)²-($\frac{1}{2}$ b)²
=(5a-$\frac{1}{2}$ b)(5a+$\frac{1}{2}$ b)
2/(a-b)²-c²
=(a-b-c)(a-b+c)
3/ x²+12x+36
=x²+2.x.6+6²
=(x+6)²
4/9x²-30x+25
=(3x)²-2.3x.5+5²
=(3x-5)²
5/ 8x³+27y³
=(2x)³+(3y)³
=(2x+3y)(4x²-6xy+9y²)
6/ $\frac{1}{8}$ x³-8
=($\frac{1}{2}$ x)³-2³
=($\frac{1}{2}$ x-2)($\frac{1}{2}$ x+x+4)
7/ (x+1)³-125
=(x+1)³-5³
=(x+1-5)[(x+1)²+5(x+1)+5²]
=(x-4)(x²+2x+1+5x+5+25)
=(x-4)(x²+7x+31)
8/ 125-75m+9m²-m³
(Sai đề hay sao í)
9/ 8a³+12a²+6a+1
=(2a)³+3.(2a)².1+3.2a.1²+1³
=(2a+1)³
10/ 27a³-27a²+9a-1
= (3a)³-3.(3a)².1+3.3a.1²-1³
=(3a-1)³
