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\(12x^2+7x-12\)
\(=12x^2-9x+16x-12\)
\(=3x\left(4x-3\right)+4\left(4x-3\right)\)
\(=\left(4x-3\right)\left(3x+4\right)\)
12x^2+7x-12=(12x^2-9x)+(16x-12)=3x(4x-3)+4(4x-3)=(3x+4)(4x-3)
chúc hok tốt
\(12x^2+7x-12=12x^2-5x+12x-12\)
\(=x\left(12x-5\right)+12\left(x-1\right)\)
Đề sai rồi bạn ời
12x2 + 7x - 12
= 12x2 + 16x - 9x - 12
= 4x.( 3x + 4 ) - 3.( 3x + 4 )
= ( 3x + 4 ).( 4x - 3 )
\(12x^2+7x-12\)
\(=12x^2+16x-9x-12\)
\(=4x\left(3x+4\right)-3\left(3x+4\right)\)
\(=\left(4x-3\right)\left(3x+4\right)\)
Phân tích đa thức thành nhân tử:
a) (x-1)(x-2)(x-3)(x-4)+1
b) (x2+3x+2)(x2+7x+12)+1
c) 12x2-3xy-8xz+2yz
a) \(A=\left(x-1\right)\left(x-2\right)\left(x-3\right)\left(x-4\right)+1\)
\(A=\left[\left(x-1\right)\left(x-4\right)\right]\left[\left(x-2\right)\left(x-3\right)\right]+1\)
\(A=\left(x^2-5x+4\right)\left(x^2-5x+6\right)+1\)
Đặt \(a=x^2-5x+5\)
\(\Leftrightarrow A=\left(a-1\right)\left(a+1\right)+1\)
\(\Leftrightarrow A=a^2-1^2+1\)
\(\Leftrightarrow A=a^2\)
Thay \(a=x^2-5x+5\)vào A ta có :
\(A=\left(x^2-5x+5\right)^2\)
b) \(B=\left(x^2+3x+2\right)\left(x^2+7x+12\right)+1\)
\(B=\left(x^2+x+2x+2\right)\left(x^2+3x+4x+12\right)+1\)
\(B=\left[x\left(x+1\right)+2\left(x+1\right)\right]\left[x\left(x+3\right)+4\left(x+3\right)\right]+1\)
\(B=\left(x+1\right)\left(x+2\right)\left(x+3\right)\left(x+4\right)+1\)
Làm tương tự câu a)
c) \(12x^2-3xy-8xz+2yz\)
\(=3x\left(4x-y\right)-2z\left(4x-y\right)\)
\(=\left(4x-y\right)\left(3x-2z\right)\)
\(=\left(2x^4+6x^3\right)-\left(3x^3+9x^2\right)-\left(3x^2-9x\right)+\left(2x+6\right)\)
\(=\left(x+3\right)\left(2x^3-3x^2-3x+2\right)=\left(x+3\right)\left(2x^3-4x^2+x^2-2x-x+2\right)\)
\(=\left(x+3\right)\left(x-2\right)\left(2x^2+x-1\right)=\left(x+3\right)\left(x-2\right)\left(2x^2+2x-x-1\right)\)
\(\left(x+3\right)\left(x-2\right)\left(x+1\right)\left(2x-1\right)\)
Ta có : \(M=\left(x^2+3x+2\right)\left(x^2+7x+12\right)+1=\left(x+1\right)\left(x+2\right)\left(x+3\right)\left(x+4\right)+1\)
\(=\left[\left(x+1\right)\left(x+4\right)\right].\left[\left(x+2\right)\left(x+3\right)\right]+1=\left(x^2+5x+4\right)\left(x^2+5x+6\right)+1\)
Đặt \(t=x^2+5x+5\) \(\Rightarrow M=\left(t-1\right)\left(t+1\right)+1=t^2-1+1=t^2\)
Vậy \(M=\left(x^2+5x+5\right)^2\)
1) 3x2y+6xy+3y= 3y.(x2+2x+1) = 3y.(x+1)2
2) 12x-4x2-9+a2 = a2-(4x2-12x+9)= a2-(2x-3)2= (a+2x-3).(a-2x+3)
3) x3-7x-6 = x3-2x2+2x2-4x-3x+6 = x2.(x-2)+2x.(x-2)-3.(x-2)= (x-2).(x2+2x-3) = (x-2).(x2+x-3x-3)= (x-2).(x+1).(x-3)
1, \(12x^2+7x-12=12x^2+16x-9x-12=\left(3x+4\right)\left(4x-3\right)\)
2, \(2m^2+10m+8=2m^2+2m+8m+8=\left(2m+8\right)\left(m+1\right)\)
\(12x^2+7x-12=12x^2-9x+16x-12\)
\(=3x\left(4x-3\right)+4\left(4x-3\right)=\left(3x+4\right)\left(4x-3\right)\)
\(2m^2+10m+8=2m^2+2m+8m+8\)
\(=2m\left(m+1\right)+8\left(m+1\right)=2\left(m+4\right)\left(m+1\right)\)