câu 1 :kq của phép chia (24x^5-18x^4+30x^3):6x^3 là :
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\(6x\left(4x-5\right)-24x^2=24x^2-30x-24x^2=-30x\)
ý B
a) 3x2 .(2x2 - 3yz + x3)= 6x4 - 6x2yz +3x5
b)(24x5 - 12x4 + 6x2 ).6x2 = 144x7 - 72x6 +36x4
a) 3x2 . (2x2 - 3yz + x3)
= 3x2 . 2x2 + 3x2 . (- 3yz) + 3x2 . x3
= 6x4 + (-9x2yz) + 3x5
= 6x4 - 9x2yz + 3x5
a,ĐK: x≥4
Ta có: \(2\sqrt{x-4}-\dfrac{1}{3}\sqrt{9x-36}=4-\sqrt{x-4}\)
\(\Leftrightarrow2\sqrt{x-4}-\sqrt{x-4}=4-\sqrt{x-4}\)
\(\Leftrightarrow2\sqrt{x-4}=4\)
\(\Leftrightarrow\sqrt{x-4}=2\Leftrightarrow x-4=4\Leftrightarrow x=8\left(tm\right)\)
b, ĐK: x≥2
Ta có: \(3\sqrt{x-2}-\sqrt{x^2-4}=0\)
\(\Leftrightarrow3\sqrt{x-2}-\sqrt{\left(x-2\right)\left(x+2\right)}=0\)
\(\Leftrightarrow\sqrt{x-2}\left(3-\sqrt{x+2}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x-2}=0\\3-\sqrt{x+2}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-2=0\\\sqrt{x+2}=3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x+2=9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=7\end{matrix}\right.\)
a) (24x\(^4\)y\(^3\)- 30\(x^5y^2\)- 6 \(x^6y^3\)) : 6\(x^4y^2\)
= (24\(x^4y^3\): 6\(x^4y^2\)) - (30\(x^5y^2\): 6\(x^4y^2\)) - (6\(x^6y^3\): 6\(x^4y^2\))
= 4y - 5x - x\(^2\)y
b) (x-3)(x+3)- (x-2)(x+1)
= x\(^2\)- 9 - (x\(^2\)+x-2x-2)
= x\(^2\)- 9 (x\(^2\)- x -2)
= x\(^2\)- 9 -x\(^2\)+ x+2
= -7+x
mk chỉ phân tích thôi bạn tự chia nha!
a, \(16x^4-81=(4x^2)^2-9^2=(4x^2-9)(4x^2+9)\)
\(=[(2x)^2-3^2](4x^2+9)\)
\(=(2x+3)(2x-3)(4x^2+9)\)
b, \(x^3-3x^2+3x-1=(x-1)^3\)
\(x^2-2x+1=(x-1)^2\)
c, \(18x^5+9x^4+3x^3+6x^2+3x+1=(18x^5+9x^4+3x^3)+(6x^2+3x+1)\)
\(=(6x^2+3x+1)(3x^3+1)\)
câu c bạn đánh sai 1 dấu phép toán kìa!!!!
\(\left(18x^4y^3-24x^3y^4+12x^3y^3\right):\left(-6x^2y^3\right)=\left[18x^4y^3:\left(-6x^2y^3\right)\right]-\left[24x^3y^4:\left(-6x^2y^3\right)\right]+\left[12x^3y^3:\left(-6x^2y^3\right)\right]=-3x^2-\left(-4xy\right)+\left(-2x\right)=-3x^2+4xy-2x\)
Sửa đề: \(\dfrac{3}{x^2+6x+9}-\dfrac{3}{x^2-6x+9}+\dfrac{x^2+30x-27}{x^4-18x^2+81}\)
\(=\dfrac{3x^2-18x+27-3x^2-18x-27+x^2+30x-27}{\left(x+3\right)^2\cdot\left(x-3\right)^2}\)
\(=\dfrac{x^2-6x-27}{\left(x+3\right)^2\cdot\left(x-3\right)^2}=\dfrac{\left(x-9\right)\left(x+3\right)}{\left(x+3\right)^2\cdot\left(x-3\right)^2}\)
\(=\dfrac{\left(x-9\right)}{\left(x^2-9\right)\left(x-3\right)}\)
1: \(x^4-4+2x^3-4x\)
\(=\left(x^2-2\right)\left(x^2+2\right)+2x\left(x^2-2\right)\)
\(=\left(x^2-2\right)\left(x^2+2x+2\right)\)
4: \(-6x^3+18x^2+60x\)
\(=-6x\left(x^2-3x-10\right)\)
\(=-6x\left(x-5\right)\left(x+2\right)\)
6: \(x^4+x^3-5x^2-5x\)
\(=x\left(x^3+x^2-5x-5\right)\)
\(=x\left(x+1\right)\left(x^2-5\right)\)
`(24x^5-18x^4+30x^3) \div 6x^3`
`= 24x^5 \div 6x^3 -18x^4 \div 6x^3 + 30x^3 \div 6x^3`
`= 4x^2-3x+5`