Chia đa thức sau:
(-8a3 + 48a2b - 96ab2 + 64b3 ) : ( a - 2b )
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a) Kết quả ( a – b ) 2 .
Gợi ý a 4 – 2 a 2 b 2 + b 4 = ( a 2 – b 2 ) 2 = ( a – b ) 2 ( a + b ) 2 .
b) Kết quả - 8 ( a – 2 b ) 2 .
a) Áp dụng HĐT 5 thu được ( 2 a - 3 b ) 3 .
b) Ta có 8 x 3 + 12 x 2 y + 6 xy 2 + y 3 = ( 2 x + y ) 3 .
Áp dụng HĐT 7 với A = 2x + y; B = z
( 2 x + y ) 3 - z 3 = (2x + y - z)(4 x 2 + y 2 + z 2 + 4xy + 2xz + zy).
b) 8a3 + 4a2b - 2ab2 – b3 = (8a3 – b3 ) + (4a2b - 2ab2 )
= (2a – b)(4a2 + 2ab + b2) + 2ab(2a – b)
= (2a – b)( 4a2 + 2ab + b2 + 2ab) = (2a – b)(2a + b)2
d) (8a3 – 27b3) – 2a(4a2 – 9b2)
= (2a – 3b)(4a2 + 6ab + 9b2) – 2a(2a – 3b)(2a + 3b)
= (2a – 3b)(4a2 + 6ab + 9b2 – 4a2 – 6ab) = 9b2(2a – 3b)
a: =>2x^3-4x^2-3x^2+6x+4x-8+a+8 chia hết cho x-2
=>a+8=0
=>a=-8
b: =>2x^3+x^2-x^2-0,5x-0,5x+0,25+m-0,25 chia hết cho 2x+1
=>m-0,25=0
=>m=0,25
a=-5va b=-3.vậy 3a-2b=-9. ckac ckan đúg lun mjk moj lam mak
a) \(20a^4b^5c^2:\left(-5ab^2c\right)^2=20a^4b^5c^2:\left(25a^2b^4c^2\right)=\dfrac{4}{5}a^2b\)
b) \(\left(-15x^2y^3\right)^7:\left(15xy^3\right)^6-\left(32x^{18}y^5\right):\left(-4x^5y\right)^2=-15x^8y^3-2x^8y^3=-17x^8y^3\)
c) \(-13-13x^5y^2:\left(-2xy\right)-\left(x^2+2x+1\right):\left(x+1\right)=-13+\dfrac{13}{2}x^4y-\left(x+1\right)^2:\left(x+1\right)=-13+\dfrac{13}{2}x^4y-x-1=-14+\dfrac{13}{2}x^4y-x\)
a: \(\dfrac{20a^4b^5c^2}{\left(-5ab^2c\right)^2}=\dfrac{20a^4b^5c^2}{25a^2b^4c^2}=\dfrac{4}{5}a^2b\)
b: \(\dfrac{\left(-15x^2y^3\right)^7}{\left(15xy^3\right)^6}-\dfrac{\left(32x^{18}y^5\right)}{\left(-4x^5y\right)^2}\)
\(=\dfrac{\left(-15\right)^7\cdot x^{14}\cdot y^{21}}{15^6\cdot x^6\cdot y^{18}}-\dfrac{32x^{18}y^5}{16x^{10}y^2}\)
\(=-15x^8y^3-2x^8y^3\)
\(=-17x^8y^3\)
b)
Sửa đề: \(125a^3+75a^2+15a+1\)
Ta có: \(125a^3+75a^2+15a+1\)
\(=\left(5a\right)^3+3\cdot\left(5a\right)^2\cdot1+3\cdot5a\cdot1^2+1^3\)
\(=\left(5a+1\right)^3\)
c) Ta có: \(64-96a+48a^2-8a^3\)
\(=-\left(8a^3-48a^2+96a-64\right)\)
\(=-\left[\left(8a^3-64\right)-48a\left(a-2\right)\right]\)
\(=-\left[\left(2a-4\right)\left(4a^2+8a+16\right)-48a\left(a-2\right)\right]\)
\(=-\left[\left(a-2\right)\left(8a^2+16a+32-48a\right)\right]\)
\(=-\left(a-2\right)\left(8a^2-32a+32\right)\)
\(=-8\left(a-2\right)\left(a^2-4a+4\right)\)
\(=-8\left(a-2\right)^3\)
(-8a3 + 48a2b - 96ab2 + 64b3 ) : ( a - 2b )
= -8( a3 - 6a2b + 12ab2 - 8b3) : ( a -2b)
= -8(a - 2b)3 : (a -2b)
= -8 (a2 - 4ab + 4b2)
= -8a2 + 32ab - 32b2