Theo bài ra , ta có : 

x² - 6x + 8 =0 

(=) x² - 2x - 4x + 8 = 0 

(=) x(x-2) - 4(x-2) = 0 

(=) (x-2)(x-4) = 0 

\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\x-4=0\end{cases}}\)  \(\Leftrightarrow\orbr{\begin{cases}x=2\\x=4\end{cases}}\)

Vậy x=2;x=4

-6 nha bạn nhớ 

x(x+1)-x(x-3)=0

=>x²+x-x²+3x=0

=>4x=0

=>x=0

vậy x=0 thì x(x+1)-x(x-3)=0

\(xyz\left(\frac{1}{x}+\frac{1}{y}+\frac{1}{z}\right)=0\\ \Rightarrow yz+xz+xy=0\)

\(A=\frac{xy}{z^2}+\frac{xz}{y^2}+\frac{yz}{x^2}\\ \Leftrightarrow A=\frac{x^3y^3+x^3z^3+y^3z^3}{x^2y^2z^2}\)

Ta có :\(yz+xz+xy=0\)

         \(\Rightarrow y^3x^3+x^3z^3+x^3y^3=-3xyz\left(y^2z+yz^2+x^2z+xz^2+x^2y+xy^2+2xyz\right)\)

                                                  \(=-3xyz\left(yz+xz\right)\left(xz+xy\right)\left(yz+xy\right)\)

                                                   \(=-3xyz\left(-xy\right)\left(-yz\right)\left(-xz\right)\\ =3x^2y^2z^2\)

      \(\Rightarrow A=\frac{3x^2y^2z^2}{x^2y^2z^2}=3\)

Ta có: \(\left(15x-6x+7\right):\left(2x+1\right)=5\)

Áp dụng định lý Bozout, ta có:

\(f\left(\frac{-1}{2}\right)=15\cdot\frac{-1}{2}-6\cdot\frac{-1}{2}+7=\frac{5}{2}\)

Vậy số dư là 2,5

\(\frac{2a+2}{3}+\frac{a-8}{3}=b\)

\(\frac{2a+2+a-8}{3}=b\)

\(\frac{3a-6}{3}=b\)

\(\frac{3\left(a-2\right)}{3}=b\)

a - 2               = b

a - b             = 2

SADC=31*4=124

\(S=\frac{1}{10.11}+\frac{1}{11.12}+...+\frac{1}{99.100}\)

\(\Rightarrow S=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+...+\frac{1}{99}-\frac{1}{100}\)

\(\Rightarrow S=\frac{1}{10}-\frac{1}{100}\)

\(\Rightarrow S=\frac{99}{100}\)

\(S=\frac{1}{10.11}+\frac{1}{11.12}+....+\frac{1}{99.100}\)

\(=\frac{11-10}{10.11}+\frac{12-11}{11.12}+...+\frac{100-99}{99.100}\)

\(=\frac{11}{10.11}-\frac{10}{10.11}+\frac{12}{11.12}-\frac{11}{11.12}+....+\frac{100}{99.100}-\frac{99}{99.100}\)

\(=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+....+\frac{1}{99}-\frac{1}{100}\)

\(=\frac{1}{10}-\frac{1}{100}=\frac{9}{100}\)

\(\frac{a}{b}=\frac{4}{7}\Rightarrow a=\frac{4}{7}b\)

\(a.b=700\Rightarrow\frac{4}{7}.b.b=700\Rightarrow4.b.b=7.7.100\Rightarrow b.b=\frac{7.7.4.25}{4}=7.7.5.5\)

=> b=35

a=20

DS=35

x/y+3.y/x=4

đặt b=y/x<1

1/b+3b=4

3b^2-4b+1=0

b=1loia

b=1/3

(2+5b)/(1-2.b)

\(P=\frac{2+5.\frac{1}{3}}{1-2.\frac{1}{3}}=\frac{\frac{11}{3}}{\frac{1}{3}}=11\)

11 nha bạn

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