a] 29 -2 x [ X -3 ] = 5 B] 2 X CONG X = 9 C] 1 CONG 3 CONG 5 CONG ................ CONG [ 2x X CONG 1 ] = 169 ...
Đọc tiếp
a] 29 -2 x [ X -3 ] = 5 B] 2 X CONG X = 9 C] 1 CONG 3 CONG 5 CONG ................ CONG [ 2x X CONG 1 ] = 169
Trả lời:
A,\(29-2\times\left(x-3\right)=5\)
\(\Leftrightarrow2\times\left(x-3\right)=24\)
\(\Leftrightarrow x-3=12\)
\(\Leftrightarrow x=15\)
Vậy \(x=15\)
B,\(2x+x=9\)
\(\Leftrightarrow3x=9\)
\(\Leftrightarrow x=3\)
Vậy \(x=3\)
C,\(1+3+5+...+\left(2x+1\right)=169\)
\(\Leftrightarrow\left(2x+1+1\right)\times\left[\left(2x+1-1\right)\div2+1\right]\div2=169\)
\(\Leftrightarrow\left(2x+2\right)\times\left(x+1\right)\div2=169\)
\(\Leftrightarrow2\times\left(x+1\right)\times\left(x+1\right)\div2=169\)
\(\Leftrightarrow\left(x+1\right)^2=169\)
\(\Leftrightarrow x+1=13\)
\(\Leftrightarrow x=12\)
Vậy \(x=12\)