Phân tích thành nhân tử : \(15a^3+16a^2-29a+2\)
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E = x^3 - 3x^2 + 7x^2 - 21x - 8x + 24
= x^2 ( x- 3 ) + 7x ( x- 3 ) - 8 ( x- 3 )
= ( x- 3 )(x^2 + 7x - 8 )
= ( x- 3 )[ x^2 + 8x - x - 8 )
= ( x -3 ) [ x(x + 8 ) - ( x + 8 ) ]
= ( x- 3 )( x - 1 )( x + 8)
=a3-3a2+7a2-21a-8a+24
=a2(a-3)+7a(a-3)-8(a-3)
=(a-3)(a2+7a-8)
=(a-3)(a2-a+8a-8)
=(a-3)(a+8)(a-1)
\(\left(a+4\right)^2-16a^2\)
\(=\left(a+4\right)^2-\left(4a\right)^2\)
\(=\left(a+4+4a\right)\left(a+4-4a\right)\)
\(=\left(5a+4\right)\left(4-3a\right)\)
\(x^3=4x\)
\(\Leftrightarrow x^3-4x=0\)
\(\Leftrightarrow x\left(x^2-4\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x^2-4=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\pm\sqrt{4}=\pm2\end{cases}}\)
16ab + 4b2 - 9 + 16a2
= (16a2 + 16ab + 4b2) - 9
= (4a+2b)2 - 32
= (4a+2b-3)(4a+2b+3)
a) \(10x^2+10xy-x-y=10x\left(x+y\right)-\left(x+y\right)=\left(x+y\right)\left(10x-1\right)\)
Lời giải:
a.
\(-16a^4b^6-24a^5b^5-9a^6b^4=-[(4a^2b^3)^2+2.(4a^2b^3).(3a^3b^2)+(3a^3b^2)^2]\)
\(=-(4a^2b^3+3a^3b^2)^2=-[a^2b^2(4b+3a)]^2\)
\(=-a^4b^4(3a+4b)^2\)
b.
$x^3-6x^2y+12xy^2-8x^3$
$=x^3-3.x^2.2y+3.x(2y)^2-(2y)^3=(x-2y)^3$
c.
$x^3+\frac{3}{2}x^2+\frac{3}{4}x+\frac{1}{8}$
$=x^3+3.x^2.\frac{1}{2}+3.x.\frac{1}{2^2}+(\frac{1}{2})^3$
$=(x+\frac{1}{2})^3$
a) Ta có: \(-16a^4b^6-24a^5b^5-9a^6b^4\)
\(=-a^4b^4\left(16b^2+24ab+9a^2\right)\)
\(=-a^4b^4\cdot\left(4b+3a\right)^2\)
b) Ta có: \(x^3-6x^2y+12xy^2-8y^3\)
\(=x^3-3\cdot x^2\cdot2y+3\cdot x\cdot\left(2y\right)^2-\left(2y\right)^3\)
\(=\left(x-2y\right)^3\)
c) Ta có: \(x^3+\dfrac{3}{2}x^2+\dfrac{3}{4}x+\dfrac{1}{8}\)
\(=x^3+3\cdot x^2\cdot\dfrac{1}{2}+3\cdot x\cdot\left(\dfrac{1}{2}\right)^2+\left(\dfrac{1}{2}\right)^3\)
\(=\left(x+\dfrac{1}{2}\right)^3\)
a) \(27x^3-0,001\)
\(=\left(3x\right)^3-\left(\frac{1}{10}\right)^3\)
\(=\left(3x-\frac{1}{10}\right)\left(9x^2+\frac{3}{10}x+\frac{1}{100}\right)\)
b) \(a^4-2a^2+1\)
\(=\left(a^2\right)^2-2a^2+1\)
\(=\left(a^2-1\right)^2\)
c)\(\left(a^2+4\right)^2-16a^2\)
\(=\left(a^2+4\right)^2-\left(4a\right)^2\)
\(=\left(a^2+4-4a\right)\left(a^2+4+4a\right)\)
\(=\left(a-2\right)^2\left(a+2\right)^2\)
\(=\left(-5a\right)^3+3.\left(-5a\right)^2+3.\left(-5a\right)+1\)
\(=\left(-5a+1\right)^3\)
\(15a^3+16a^2-29a+2\)
\(=\left(15a^3-15a^2\right)+\left(31a^2-31a\right)-\left(2a-2\right)\)
\(=\left(a-1\right)15a^2+31a\left(a-1\right)-2\left(a-1\right)\)
\(=\left(a-1\right)\left(15a^2+31a-2\right)\)
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