Nội dung bài giảng
Tìm x, biết rằng:
a) 3.(10.x)=111
b) 3.(10+x) =111
c) 3 + (10.x) = 111
d) 3 + (10 + x) = 111
Giải
\(a)3.\left( {10.x} \right) = 111\) \( \Leftrightarrow \left( {10.x} \right) = 111:3\)
\( \Leftrightarrow 10.x = 37\) \( \Leftrightarrow x = 37:10 = 3,7\)
\(b)3.\left( {10 + x} \right){\rm{ }} = 111\) \( \Leftrightarrow (10 + x) = 111:3\)
\( \Leftrightarrow 10 + x = 37\) \( \Leftrightarrow x = 37 - 10 = 27\)
\(c)3 + \left( {10.x} \right) = 111\) \( \Leftrightarrow (10.x) = 111 - 3\)
\( \Leftrightarrow 10.x = 108\) \( \Leftrightarrow x = 108:10 = 10,8\)
\(d){\rm{ }}3{\rm{ }} + {\rm{ }}\left( {10{\rm{ }} + {\rm{ }}x} \right){\rm{ }} = {\rm{ }}111\)
\( \Leftrightarrow (10 + x) = 111 - 3\)
\( \Leftrightarrow 10 + x = 108\) \(\Leftrightarrow x = 108 - 10 = 98\)