1/\(9x^2+6x-575=\left(3x\right)^2+2.3x.1+1-576=\left(3x+1\right)^2-24^2=\left(3x-23\right)\left(3x+25\right)\)
2/\(81x^4+4=81x^4+36x^2+4-36x^2=\left(9x^2+2\right)^2-\left(6x\right)^2\)
\(=\left(9x^2-6x+2\right)\left(9x^2+6x+2\right)\)
3/đặt \(t=x^2+8x+7\) thì đa thức cần phân tích:
t(t+8)+15=t2+8t+15=t2+3t+5t+15=t(t+3)+5(t+3)=(t+3)(t+5)=(x2+8x+10)(x2+8x+12)=(x2+8x+10)(x2+2x+6x+12)
=(x2+8x+10)[x(x+2)+6(x+2)]=(x2+8x+10)(x+2)(x+6)
tạm thế này đã, phải đi ăn cơm rồi :v
Giups hộ cj My :))
4 ) Đặt \(12x^2+11x-1=a\)
\(\left(4x+1\right)\left(12x-1\right)\left(3x+2\right)\left(x+1\right)-4\)
\(=\left(12x^2+11x+2\right)\left(12x^2+11x-1\right)-4\)
\(=\left(a-3\right)a-4=a^2-3a-4=a^2-4a+a-4=a\left(a-4\right)+\left(a-4\right)\)
\(=\left(a+1\right)\left(a-4\right)=\left(12x^2+11x\right)\left(12x^2+11x-5\right)=x\left(12x+11\right)\left(4x+5\right)\left(3x-1\right)\)
Á quên ý 5
\(x^3+x^2-10x+8\)
\(=x^3-x^2+2x^2-2x-8x+8\)
\(=x^2\left(x-1\right)+2x\left(x-1\right)-8\left(x-1\right)\)
\(=\left(x^2+2x-8\right)\left(x-1\right)\)
\(=\left(x^2-2x+4x-8\right)\left(x-1\right)\)
\(=\left[x\left(x-2\right)+4\left(x-2\right)\right]\left(x-1\right)\)
\(=\left(x+4\right)\left(x-2\right)\left(x-1\right)\)
Phân tích các đa thức sau thành nhân tử :
1) 9x^2 +6x -575
2) 81x^4 + 4
3) (x^2 + 8x +7)(x^2 +8x +15) + 15
4) (4x +1 )(12x - 1)(3x+2)(x+1)-
