Question

tìm x

a)-(2x + 15 ) + 13 = -234

b)2+4+6+8 +..............+2x=182

Answer 1

a)-(2x + 15 ) + 13 = -234

\(\Leftrightarrow\)-2x-15+13+234=0

\(\Leftrightarrow\)2x=232

\(\Leftrightarrow\)x=116

b)2+4+6+8 +..............+2x=182

\(\Leftrightarrow\)2(1+2+3+4+.....+x) =182

\(\Leftrightarrow\)1+2+3+4+.....+x= 182/2 = 91

\(\Leftrightarrow\)x(x+1)/2 =91

\(\Leftrightarrow\)x(x+1)= 182

\(\Leftrightarrow\)x(x+1) = 13(13+1)

\(\Leftrightarrow\)\(\hept{\begin{cases}x=13\\x+1=13+1\end{cases}}\Leftrightarrow x=13\)

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