viết thành tích:
16x^3+27
Giúp vs...
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\(a,=\left(3+x\right)\left(9-3x+x^2\right)\\ b,=\left(4x+0,1\right)\left(16x^2-0,4x+0,01\right)\\ c,=\left(2-3x\right)\left(4+6x+9x^2\right)\\ d,=\left(\dfrac{x}{5}-\dfrac{y}{3}\right)\left(\dfrac{x^2}{25}+\dfrac{xy}{15}+\dfrac{y^2}{9}\right)\)
a: \(\dfrac{x}{6}=\dfrac{8}{3}\)
=>\(x=6\cdot\dfrac{8}{3}=\dfrac{6}{3}\cdot8=8\cdot2=16\)
b: \(\dfrac{5}{x}=\dfrac{4}{9}\)
=>\(x=\dfrac{5\cdot9}{4}=\dfrac{45}{4}\)
c: \(\dfrac{x+3}{-4}=\dfrac{5}{20}\)
=>\(x+3=\dfrac{-4\cdot5}{20}=-1\)
=>x=-1-3=-4
d: \(\dfrac{7}{3+4x}=\dfrac{-2}{9}\)
=>\(4x+3=\dfrac{9\cdot7}{-2}=-\dfrac{63}{2}\)
=>\(4x=-\dfrac{63}{2}-3=-\dfrac{69}{2}\)
=>\(x=-\dfrac{69}{8}\)
f: ĐKXĐ: x<>1
\(\dfrac{3}{x-1}=\dfrac{x-1}{27}\)
=>\(\left(x-1\right)^2=3\cdot27=81\)
=>\(\left[{}\begin{matrix}x-1=9\\x-1=-9\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=10\left(nhận\right)\\x=-8\left(nhận\right)\end{matrix}\right.\)
16 x - 5 x 2 - 3 = 15 x - 5 x 2 - 3 + x = 15 x - 5 x 2 - 3 - x = 5 x 3 - x - 3 - x = 3 - x 5 x - 1
\(=-5x^2+15x+x-3=-5x\left(x-3\right)+\left(x-3\right)=\left(1-5x\right)\left(x-3\right)\)
\(16x^3+54y^3\)
\(=2\left(8x^3-27y^3\right)\)
\(=2.\left(2x-3y\right)\left(4x^2-6xy+9y^2\right)\)
\(=\left(x-3\right)\left(8x^3-16x^2\right)=8x^2\left(x-2\right)\left(x-3\right)\)
\(8x^3\left(x-3\right)+16x^2\left(3-x\right)\)
\(=8x^3\left(x-3\right)-16x^2\left(x-3\right)\)
\(=8x^2\left(x-3\right)\left(x-2\right)\)
16x3+27
=(\(\sqrt{16}\)x)3+33
=\(\left(\sqrt{16}x+3\right)\left[\left(\sqrt{16}x\right)^2-3.\sqrt{16}x+9\right]\)