Ai bt =)))

a)58.(-73)=58.(-27)                                                                                           =58.[(-73)+(-27)]                                                                                               =58.(-100)                                                                                                         =(-5800)      

58.(-73)+58.(-27)

=58.-[73+27]

=58.(-100)

=(-5800)

\(a,\left|x+2\right|=0\)

\(\Leftrightarrow x+2=0\)

\(\Leftrightarrow x=-2\)

\(b,\left|x-5\right|=\left|-7\right|\)

\(\Leftrightarrow\left|x-5\right|=7\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=7\\x-5=-7\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-2\end{matrix}\right.\)

\(c,\left(7-x\right)-\left(25+7\right)=-25\)

\(\Leftrightarrow7-x-32=-25\)

\(\Leftrightarrow x=0\)

\(d,\left|x-3\right|=\left|5\right|+\left|-7\right|\)

\(\Leftrightarrow\left|x-3\right|=12\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=12\\x-3=-12\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=15\\x=-9\end{matrix}\right.\)

\(B=1-5+5^{^2}-5^{^3}+...-5^{^{99}}+5^{^{100}}\)

\(5B=5-5^{^2}+5^{^3}-5^{^4}+...-5^{^{100}}+5^{^{101}}\)

\(5B+B=\left(5-5^{^2}+5^{^3}-5^{^4}+...-5^{^{100}}+5^{^{101}}\right)+\left(1-5+5^{^2}-5^{^3}+...-5^{^{99}}+5^{^{100}}\right)\)

\(6B=5^{^{101}}+1\)

\(B=\dfrac{5^{^{101}}+1}{6}\)

= 1

tick đi mink giải thích cho .  hihihihihihihihiihihiiiiiiiiiiiiiiii

A = \(\dfrac{1}{1+2}\) + \(\dfrac{1}{1+2+3}\) + ... + \(\dfrac{1}{1+2+3+...+99}\) + \(\dfrac{1}{50}\)

A = \(\dfrac{1}{\left(2+1\right).2:2}\) + \(\dfrac{1}{\left(3+1\right).3:2}\) + ... + \(\dfrac{1}{\left(99+1\right).99:2}\) + \(\dfrac{1}{50}\)

A = \(\dfrac{2}{2.3}\) + \(\dfrac{2}{3.4}\) + \(\dfrac{2}{4.5}\) + ... + \(\dfrac{2}{99.100}\) + \(\dfrac{1}{50}\)

A = 2.(\(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) + \(\dfrac{1}{4.5}\) + ... + \(\dfrac{1}{99.100}\)) + \(\dfrac{1}{50}\)

A = 2.(\(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + \(\dfrac{1}{3}\) - \(\dfrac{1}{4}\)  + \(\dfrac{1}{4}-\dfrac{1}{5}\)+ \(\dfrac{1}{5}\) - \(\dfrac{1}{6}\) + ... + \(\dfrac{1}{99}\) - \(\dfrac{1}{100}\)) + \(\dfrac{1}{50}\)

A = 2.(\(\dfrac{1}{2}\) - \(\dfrac{1}{100}\)) + \(\dfrac{1}{50}\)

A = 2.(\(\dfrac{50}{100}\) - \(\dfrac{1}{100}\)) + \(\dfrac{1}{50}\)

A = 2.\(\dfrac{49}{100}\) + \(\dfrac{1}{50}\)

A = \(\dfrac{49}{50}\) + \(\dfrac{1}{50}\)

A = 1

\(a_{n-1}=\frac{1}{1+2+..+n}=\frac{2}{n\left(n+1\right)}=\frac{2}{n}-\frac{2}{n+1}\)

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

\(=1-\frac{1}{50}=\frac{49}{50}\)

chtt

tặng cho mk vài li-ke nha

\(1\times\left(1+1\right)+2\times\left(2+1\right)+3\times\left(3+1\right)\)

\(=1\times2+2\times3+3\times4\)

\(=2+6+12\)

\(=20\)

\(a=215\times62+42-52\times215\)

\(a=215\times\left(62-52\right)+42\)

\(a=215\times10+42\)

\(a=2150+42\)

\(a=2192\)

\(b=14\times29+14\times71+\left(1+2+3+...+99\right)\times\left(199199\times198-198198\times199\right)\)

\(b=14\times\left(29+71\right)+\left(1+2+3+...+99\right)\times\left(199\times1001\times198-198\times1001\times199\right)\)

\(b=14\times100+0\)

\(b=1400\)

1: Quá dễ

1 . (1 + 1) + 2 . (2 + 1) + 3 . (3 + 1)

= 1 . 2 + 2 . 3 + 3 . 4

= 2 + 6 + 12

= 20

2:

a = 215 . 62 + 42 - 52 . 215

= 215 . (62 - 52) + 42

= 215 . 10 + 42

= 2150 + 42

= 2192

b = 14 . 29 + 14 . 71 + (1 + 2 + 3 + ... + 99) . (199199 . 198 - 198198 . 199)

= 14 . (29 + 71) + (1 + 2 + 3 + ... + 99) . (199 . 1001 . 198 - 198 . 1001 . 199)

= 14 . 100 + (1 + 2 + 3 + ... + 99) . 0

= 1400 + 0 = 1400