\(a^2=bc\)

\(\Leftrightarrow2a^2=2bc\)

\(\Leftrightarrow ac-ab+2a^2=2bc+ac-ab\)

\(\Leftrightarrow ac+bc-a^2-ab=a^2-ab+ac-bc\)

\(\Leftrightarrow c\left(a+b\right)-a\left(a+b\right)=a\left(a-b\right)+c\left(a-b\right)\)

\(\Leftrightarrow\left(c-a\right)\left(a+b\right)=\left(a+c\right)\left(a-b\right)\)

\(\Leftrightarrow\frac{a+b}{a-b}=\frac{a+c}{c-a}\)

Ta có: a²=b.c

->  a/c=b/a = a+b/c+a = a-b/c-a

-> a+b/a-b= c+a/c-a

\(\Rightarrow x.8=-2.5\)

\(\Rightarrow x.8=-10\)

\(\Rightarrow x=-\frac{5}{4}\)

\(\frac{x}{-2}=\frac{5}{8}\)

\(\Leftrightarrow8x=-10\)

\(\Leftrightarrow x=\frac{-5}{4}\)

\(\frac{2-x}{4}=\frac{3x-1}{3}\)

\(\Leftrightarrow6-3x=12x-4\)

\(\Leftrightarrow15x=10\Leftrightarrow x=\frac{2}{3}\)

\(\Rightarrow\left(2-x\right).3=\left(3x-1\right).4\)

\(\Rightarrow6-3x=12x-4\)

\(\Rightarrow6-3x-12x=-4\)

\(\Rightarrow3x\left(-1-4\right)=-6-4\)

\(\Rightarrow3x.-5=-10\)

\(\Rightarrow3x=2\)

\(\Rightarrow x=\frac{2}{3}\)

GPlà điểm k của quản lí

SP là điểm k của mọi người

tk cho mik

KHÁC CHỮ G VÀ CHỮ S

Ta có

\(3x=y;\frac{y}{4}=\frac{z}{5}\Rightarrow\frac{y}{3}=\frac{x}{1};\frac{y}{4}=\frac{z}{5}\Rightarrow\frac{x}{4}=\frac{y}{12}=\frac{z}{15}\Rightarrow\frac{2x}{4}=\frac{3y}{36}=\frac{x}{15}\)

Aps dụng tính chất DTSBN ta có

\(\frac{2x}{4}=\frac{3y}{36}=\frac{x}{15}=\frac{2x-3y+z}{4-36+15}=\frac{26}{-17}\)

\(\hept{\begin{cases}\frac{x}{4}=-\frac{26}{17}\\\frac{y}{12}=-\frac{26}{17}\\\frac{z}{15}=-\frac{26}{17}\end{cases}\Rightarrow\hept{\begin{cases}x=-\frac{104}{17}\\y=-\frac{312}{17}\\z=-\frac{390}{17}\end{cases}}}\)

Bài làm

Vì \(3x=y\Rightarrow x=\frac{y}{3}=\frac{x}{4}=\frac{y}{12}\)

\(\frac{y}{4}=\frac{z}{5}\Rightarrow\frac{y}{12}=\frac{z}{15}\)

=> \(\frac{x}{4}=\frac{y}{12}=\frac{z}{15}\Rightarrow\frac{2x}{8}=\frac{3y}{36}=\frac{z}{15}\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có:

\(\frac{2x}{8}=\frac{3y}{36}=\frac{z}{15}\Rightarrow\frac{2x-3y+z}{8-36+18}=\frac{26}{-13}=-2\)

Do đó: \(\hept{\begin{cases}\frac{x}{4}=-2\\\frac{y}{12}=-2\\\frac{z}{15}=-2\end{cases}\Rightarrow\hept{\begin{cases}x=-8\\y=-24\\z=-30\end{cases}}}\)

Vậy x = -8, y = -24, z = -30

# Học tốt #

ko đăng linh tinh

ko đăng linh tinh 

Có (x + 15) ⋮ (x - 1)

<=> x - 1 + 16 ⋮ x - 1

<=> 16 ⋮ x - 1 (Vì x - 1 ⋮ x - 1)

<=> x - 1 ∈ Ư(16)

<=> x - 1 ∈ {1; 2; 4; 8; 16; -1; -2; -4; -8; -16}

<=> x ∈ {2; 3; 5; 9; 17; 0; -1; -3; -7; -15}

Mà x ∈ N => x ∈ {2;3;5;9;17;0}

\(A=\frac{1}{3}-\frac{1}{3^2}+\frac{1}{3^3}-\frac{1}{3^4}+...+\frac{1}{3^{99}}-\)\(\frac{1}{3^{100}}\)

=> \(\frac{1}{3}A=\frac{1}{3^2}-\frac{1}{3^3}+\frac{1}{3^4}-\frac{1}{3^5}+...+\frac{1}{3^{100}}-\frac{1}{3^{101}}\)

=> \(A+\frac{1}{3}A=\frac{1}{3}-\frac{1}{3^2}+...+\frac{1}{3^{99}}-\frac{1}{3^{100}}\)\(+\frac{1}{3^2}-\frac{1}{3^3}+...+\frac{1}{3^{100}}-\frac{1}{3^{101}}\)

=>\(\frac{4}{3}A=\frac{1}{3}-\frac{1}{3^{101}}\)

=>\(A=\frac{1}{4}-\frac{1}{3^{100}.4}\)