88-3.(7+x)=64

3(7+x) = 88-64

3(7+x) = 24

7+x = 24:3

7+x = 8

x= 8-7

x=1

88-3(7+x)=64

3(7+x)=88-64

3(7+x)=24

7+x=24:3

7+x=8

x=8-7

x=1

Vậy x=1

dễ

3.(7+x)=24

7+x=8

=>x=1

ta có: \(x-\frac{91}{y}=2\)

<=> \(xy-91=2y\) ( với \(y\ne0\))

<=>\(y\left(x-2\right)=91\)

đến đây tự giải đc rồi nha!

1/15

giup minh voi, di ma

\(\dfrac{1}{2}\times\left(\dfrac{1}{3}-\dfrac{1}{5}\right)=\dfrac{1}{2}\times\left(\dfrac{5}{15}-\dfrac{3}{15}\right)=\dfrac{1}{2}\times\dfrac{2}{15}=\dfrac{1}{15}\)

a: Ta có: \(A=1+3^2+3^4+\cdots+3^{100}\)

\(=\left(1+3^2+3^4\right)+\left(3^6+3^8+3^{10}\right)+\cdots+\left(3^{96}+3^{98}+3^{100}\right)\)

\(=\left(1+3^2+3^4\right)+3^6\left(1+3^2+3^4\right)+\cdots+3^{96}\left(1+3^2+3^4\right)=91\left(1+3^6+\cdots+3^{96}\right)\) ⋮91

b: Ta có: \(A=1+3^2+3^4+\cdots+3^{100}\)

=>\(9A=3^2+3^4+3^6+\cdots+3^{102}\)

=>\(9A-A=3^2+3^4+\cdots+3^{102}-1-3^2-\cdots-3^{100}\)

=>\(8A=3^{102}-1\)

=>\(8A+1=3^{102}\)

=>\(8A+1=\left(3^{51}\right)^2\) là số chính phương

to lop 5 chiu thoi

mày có bình thường không đấy ?

\(\frac{2}{3}=\frac{2\times18}{3\times18}=\frac{36}{54}\)

\(\Rightarrow x=36\)

~ Chúc bạn học tốt ~

\(\frac{2}{3}=\frac{x}{54}\)

54 gấp 3:

54:3=18(lần)

Vậy x=18x2=36

2/3=36/54