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\(3x\left(x-5\right)-x\left(4+3x\right)=43\)
\(\Leftrightarrow3x^2-15x-4x-3x^2=43\)
\(\Leftrightarrow-19x=43\)
\(\Leftrightarrow x=\frac{-43}{19}\)
câu này mih biết làm nhưng pp nhẩm nghiệm là sao bạn
bạn có thể cho mih vd đi\ược ko
\(x^3-x^2-4x^2+8x^4\)
\(=x^3-5x^2+8x^4=x^2\left(x-5+8x^2\right)\)
\(-x^2-2x+15=-\left(x^2+2x+1-16\right)\)
\(=-\left[\left(x-1\right)^2-16\right]=-\left(x-5\right)\left(x+3\right)\)
\(3x^2+4x+1=4x^2+4x+1-x^2\)
\(=\left(2x+1\right)^2-x^2=\left(x+1\right)\left(3x+1\right)\)
\(x^4-5x^2+4\)
=\(\left(x^4-x^2\right)-\left(4x^2-4\right)\)
=\(x^2\left(x^2-1\right)-4\left(x^2-1\right)\)
=\(\left(x^2-4\right)\left(x^2-1\right)\)
\(x^2+5x-6\)
=\(x^2-x+6x-6\)
=\(x\left(x-1\right)+6\left(x-1\right)\)
=\(\left(x+6\right)\left(x-1\right)\)
2 câu cuối làm tương tự nha câu 2 nha
1.
a) \(\left(-2x^3\right)\)\(\left(x^2+5x-\frac{1}{2}\right)\) = \(-2x^5\)\(-10x^4\) \(+x^3\)
b) (\(6x^3-7x^2\)\(-x+2\))\(:\left(2x+1\right)\)=\(3x^2-5x+2\)
2.
a) 9x(3x-y) + 3y (y-3x)=9x(3x-y)-3y(3x-y)
= (9x-3y)(3x-y)
= 3(3x-y)(3x-y)
= 3(3x-y)^2
b) \(x^3-3x^2\)\(-9x+27\)= \(\left(x^3-3x^2\right)\)\(-\left(9x-27\right)\)
= \(x^2\left(x-3\right)\)\(-9\left(x-3\right)\)
= \(\left(x^2-9\right)\left(x-3\right)\)
= \(\left(x+3\right)\left(x-3\right)\left(x-3\right)\)
= \(\left(x+3\right)\left(x-3\right)^2\)
Bài 1 ) a ) \(\left(-2x^3\right)\left(x^2+5x-\frac{1}{2}\right)\)
\(=-2x^5-10x^4+x^3\)
b ) \(\left(6x^3-7x^2+x+2\right):\left(2x+1\right)\)
\(=3x^2-5x+2\)
2 ) a ) \(9x\left(3x-y\right)+3y\left(y-3x\right)\)
\(=9x\left(3x-y\right)-3y\left(3x-y\right)\)
\(=\left(3x-y\right)\left(9x-3y\right)\)
\(=3\left(3x-y\right)\left(x-y\right)\)
b ) \(x^3-3x^2-9x+27\)
\(=\left(x^3-3x^2\right)-\left(9x-27\right)\)
\(=x^2\left(x-3\right)-9\left(x-3\right)\)
\(=\left(x^2-9\right)\left(x-3\right)\)
\(=\left(x-3\right)\left(x+3\right)\left(x-3\right)\)
a) Đặt t = x2
bthuc <=> t2 - 7t + 16
Từ đây ta không thể phân tích được :)
b) x3 - 2x2 + 5x - 4
= x3 - x2 - x2 + x + 4x - 4
= x2( x - 1 ) - x( x - 1 ) + 4( x - 1 )
= ( x - 1 )( x2 - x + 4 )
c) x3 - 2x2 + x - 3 ( phân tích hổng ra :)) )
d) 3x3 - 4x2 + 12x - 4 ( phân tích hổng ra p2 :)) )
e) 6x3 + x2 + x + 1
= 6x3 + 3x2 - 2x2 - x + 2x + 1
= 3x2( 2x + 1 ) - x( 2x - 1 ) + ( 2x + 1 )
= ( 2x + 1 )( 3x2 - x + 1 )
f) 4x3 + 6x2 + 4x + 1
= 4x3 + 2x2 + 4x2 + 2x + 2x + 1
= 2x2( 2x + 1 ) + 2x( 2x + 1 ) + ( 2x + 1 )
= ( 2x + 1 )( 2x2 + 2x + 1 )
\(G=2x^2-3x+1=2x^2-2x-x+1\)
\(=2x\left(x-1\right)-\left(x-1\right)=\left(2x-1\right)\left(x-1\right)\)
\(H=-x^2+5x-4=-x^2+4x+x-4\)
\(=-x\left(x-4\right)+\left(x-4\right)=\left(1-x\right)\left(x-4\right)\)
\(I=x^2+4x+3=x^2+3x+x+3\)
\(=x\left(x+3\right)+\left(x+3\right)=\left(x+1\right)\left(x+3\right)\)
\(K=2x^2+7x+5=2x^2+2x+5x+5\)
\(=2x\left(x+1\right)+5\left(x+1\right)=\left(2x+5\right)\left(x+1\right)\)
\(L=-3x^2-5x-2=-3x^2-3x-2x-2\)
\(=-3x\left(x+1\right)-2\left(x+1\right)=\left(-3x-2\right)\left(x+1\right)\)
\(1.3x^2-x-10=3x^2+5x-6x-10=x\left(3x+5\right)-2\left(3x+5\right)=\left(3x+5\right)\left(x-2\right)\) \(2.2x^2+3x-9=2x^2-3x+6x-9=x\left(2x-3\right)+3\left(2x-3\right)=\left(2x-3\right)\left(x+3\right)\) \(3.2x^4-5x-7=2x^4+2x-7x-7=2x\left(x^3+1\right)-7\left(x+1\right)=2x\left(x+1\right)\left(x^2-x+1\right)-7\left(x+1\right)=\left(x+1\right)\left(2x^3-2x^2+2x-7\right)\)
a)
\(3x^2-x-10\)
\(\Leftrightarrow3x^2-6x+5-10\)
\(\Leftrightarrow3x\left(x-2\right)+5\left(x-2\right)\)
\(\Leftrightarrow\left(x-2\right)\left(3x+5\right)\)
b) Đề sai nha bạn, mình mạo phép sửa lại tí nghen!
\(2x^2+3x-9\)
<=>\(2x^2-3x+6x-9\)
\(\Leftrightarrow2x\left(x+3\right)-3\left(x+3\right)\)
\(\Leftrightarrow\left(x+3\right)\left(2x-3\right)\)
c)
\(2x^4-5x-7\)
\(\Leftrightarrow2x^4-2x^3-2x^2-7x+2x^3+2x^2+2x-7\)
\(\Leftrightarrow2x^4-5x-7x-7\)
\(\Leftrightarrow\left(x+1\right)\left(2x^3-2x^2+2x-7\right)\)
Chúc bạn học tốt! ^^