\(a^2=bc\)

\(\Leftrightarrow2a^2=2bc\)

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

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

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

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

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

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

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

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

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

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

\(\Leftrightarrow8x=-10\)

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

\(=81.53+19.\left(28+25\right)\)

\(=81.53+19.53\)

\(=\left(81+19\right).53\)

\(=100.53\)

\(=5300\)

81*53+19*28+19*25

=81*53+19*(28+25)

=81*53+19*53

=53*(81+19)

=53*100

=5300

Tổng số phần bằng nhau :

     3 + 5 = 8 ( phần )

Chiều dài khu vườn :

     120 : 8 x 5 = 75 ( m )

Chiều rộng khu vườn :

     120 - 75 = 45 ( m )

Diện tích khu vườn :

     75 x 45 = 3375 ( m² )

     3375 m² = 0,3375 ha

Đáp số : 3375 m² ; 0,3375 ha

mình đang cấn gấp

\(A=2+2^2+2^3+....+2^{60}\)

\(=2\left(1+2+2^2+2^3+2^4+2^5\right)+....+2^{55}\left(1+2+2^2+2^3+2^4+2^5\right)\)

\(=2\cdot63+....+2^{65}\cdot63⋮21\)

\(A=2+2^2+2^3+2^4....+2^{60}\)

\(=\left(2+2^2+2^3+2^4\right)+\left(2^5+2^6+2^7+2^8\right)+....+\left(2^{57}+2^{58}+2^{59}+2^{60}\right)\)

\(=2\left(1+2+2^2+2^3\right)+2^5\left(1+2+2^2+2^3\right)+...+2^{57}\left(1+2+2^2+2^3\right)\)

\(=2\cdot15+2^5\cdot15+...+2^{57}\cdot15⋮15\)

toán nha các bạn

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

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

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

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

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

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

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

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

\(\Rightarrow3x=2\)

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