Tính: \(\frac{12}{0,\left(2012\right)}+\frac{12}{0,0\left(2012\right)}+\frac{12}{0,00\left(2012\right)}+...+\frac{12}{0,0000000\left(2012\right)}\) (Ghi kết quả dưới dạng hỗn số)
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Tính: \(\frac{12}{0,\left(2012\right)}+\frac{12}{0,0\left(2012\right)}+\frac{12}{0,00\left(2012\right)}+...+\frac{12}{0,0000000\left(2012\right)}\) (Ghi kết quả dưới dạng hỗn số)
tính nhanh
\(\left(\frac{1}{10}-1\right).\left(\frac{1}{11}-1\right).\left(\frac{1}{12}-1\right)....\left(\frac{1}{2012}-1\right)\)
tính B
B=\(\frac{\left(\frac{3}{2}\right)^3.\left(-\frac{3}{4}\right)^2.\left(-1\right)^{2012}}{36.\frac{1}{5}.\left(\frac{2}{5}\right)^2.\left(-\frac{5}{12}\right)^3}\)
\(B=\frac{\left(\frac{2}{3}\right)^3.\left(\frac{3}{4}\right)^2.\left(-1\right)^{2012}}{36.\frac{1}{5}.\left(\frac{2}{5}\right)^2.\left(-\frac{5}{12}\right)^3}\)
\(\frac{\left(1+\frac{2012}{1}\right)\left(1+\frac{2012}{2}\right).......\left(1+\frac{2012}{100}\right)}{\left(1+\frac{1000}{1}\right)\left(1+\frac{1000}{2}\right).....\left(1+\frac{1000}{2012}\right)}\)
c\(\frac{\left(1+\frac{2012}{1}\right)\left(1+\frac{2012}{2}\right)....\left(1+\frac{2012}{1000}\right)}{\left(1+\frac{1000}{1}\right)\left(1+\frac{1000}{2}\right)....\left(1+\frac{1000}{2012}\right)}\)
Cho \(f\left(x\right)=\frac{x^3}{1-3x+3x^2}\)hãy tính giá trị biểu thức
\(A=f\left(\frac{1}{2012}\right)+f\left(\frac{2}{2012}\right)+...+f\left(\frac{2010}{2012}\right)+f\left(\frac{2011}{2012}\right)\)
Ta xét : \(f\left(x\right)+f\left(1-x\right)=\frac{x^3}{1-3x+3x^2}+\frac{\left(1-x\right)^3}{1-3\left(1-x\right)+3\left(1-x\right)^2}\)
\(=\frac{x^3}{1-3x+3x^2}+\frac{\left(1-x\right)^3}{3x^2-3x+1}=\frac{\left(x+1-x\right)\left(x^2+x^2-2x+1+x^2-x\right)}{3x^2-3x+1}=\frac{3x^2-3x+1}{3x^2-3x+1}=1\)
Áp dụng ta có :
\(A=\left[f\left(\frac{1}{2012}\right)+f\left(\frac{2011}{2012}\right)\right]+\left[f\left(\frac{2}{2012}\right)+f\left(\frac{2010}{2012}\right)\right]+...+\left[f\left(\frac{1006}{2012}\right)+f\left(\frac{1006}{2012}\right)\right]\)
\(=1+1+...+1\)(Có tất cả 1006 số 1)
\(=1006\)
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Rút gọn :
a/ \(A=\frac{\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+...+\frac{19}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{20}}\)
b/ \(B=\frac{\left(1+\frac{2012}{1}\right)\left(1+\frac{2012}{2}\right)...\left(1+\frac{2012}{1000}\right)}{\left(1+\frac{1000}{1}\right)\left(1+\frac{1000}{2}\right)...\left(1+\frac{1000}{2012}\right)}\)
\(\frac{298}{719}:\left(\frac{1}{4}+\frac{1}{12}-\frac{1}{3}\right)-\frac{2011}{2012}\)
\(\frac{298}{719}:\left(\frac{1}{4}+\frac{1}{12}-\frac{1}{3}\right)-\frac{2011}{2012}\)
\(=\frac{298}{719}:0-\frac{2011}{2012}\)
Giá trị phép tính không tồn tại
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