KẾT QUẢ\(\frac{-5585.63}{-3087}\)

CÁCH GIẢI     ĐẦU TIÊN BẠN TÍNH 49.(-113)+98.37-147 BẰNG -5585.63

                      VÀ THỨ 2 BẠN TÍNH 7³*(-9) BẰNG -3087

                      VÀ CUỐI CÙNG GHÉP LẠI VỚI NHAU

=-36,4 nha nếu đúng thì tích hộ mk

Đặt mỗi số số hạng của M là A;B

Ta quy đồng tử và mẫu của A bằng cách nhân cả tử và mẫu với 3.7.13;rồi dùng tính chất phân phối bỏ ngoặc ra.Tính toán bình thường.Khi đó A=1/7 

Tương tự với B ta quy đồng lên với 11.17.19;bỏ ngoặc đi và tính bình thường ;B=2/7

=>M=1/7+2/7-136/7=3/7-136/7=-19

Mình cũng thắc mắc câu này ;-;

Ta có:

\(\left|x-\frac{3}{4}\right|+\left|x+\frac{9}{7}\right|=\left|\frac{3}{4}-x\right|+\left|x+\frac{9}{7}\right|\ge\left|\frac{3}{4}-x+x+\frac{9}{7}\right|=\frac{57}{28}\)

=> \(28\cdot\left(\left|x-\frac{3}{4}\right|+\left|x+\frac{9}{7}\right|\right)\ge57\left(\forall x\right)\)

Dấu "=" xảy ra khi: \(\left(\frac{3}{4}-x\right)\left(x+\frac{9}{7}\right)\ge0\Rightarrow-\frac{9}{7}\le x\le\frac{3}{4}\)

Vậy \(Min=28\Leftrightarrow-\frac{9}{7}\le x\le\frac{3}{4}\)

Đặt \(A=\left|x-\frac{3}{4}\right|+\left|x+\frac{9}{7}\right|\)

\(\Rightarrow A=\left|\frac{3}{4}-x\right|+\left|x+\frac{9}{7}\right|\ge\left|\frac{3}{4}-x+x+\frac{9}{7}\right|=\left|\frac{57}{28}\right|=\frac{57}{28}\)

Dấu " = " xảy ra \(\Leftrightarrow\left(\frac{3}{4}-x\right)\left(x+\frac{9}{7}\right)\ge0\)

TH1: \(\hept{\begin{cases}\frac{3}{4}-x\le0\\x+\frac{9}{7}\le0\end{cases}}\Leftrightarrow\hept{\begin{cases}\frac{3}{4}\le x\\x\le\frac{-9}{7}\end{cases}}\Leftrightarrow\hept{\begin{cases}x\ge\frac{3}{4}\\x\le\frac{-9}{7}\end{cases}}\)( vô lý )

TH2: \(\hept{\begin{cases}\frac{3}{4}-x\ge0\\x+\frac{9}{7}\ge0\end{cases}}\Leftrightarrow\hept{\begin{cases}\frac{3}{4}\ge x\\x\ge\frac{-9}{7}\end{cases}}\Leftrightarrow\hept{\begin{cases}x\le\frac{3}{4}\\x\ge\frac{-9}{7}\end{cases}}\Leftrightarrow\frac{-9}{7}\le x\le\frac{3}{4}\)

\(\Rightarrow28.\left(\left|x-\frac{3}{4}\right|+\left|x+\frac{9}{7}\right|\right)\ge28.\frac{57}{28}=57\)

Dấu " = " xảy ra \(\Leftrightarrow-\frac{9}{7}\le x\le\frac{3}{4}\)

Vậy GTNN của biểu thức đã cho là \(57\)\(\Leftrightarrow-\frac{9}{7}\le x\le\frac{3}{4}\)

f) \(\left(1:\frac{1}{7}\right)^2\left[\left(2^2\right)^3:2^5\right]\cdot\frac{1}{49}\)

\(=\left(1\cdot7\right)^2:\left(2^6:2^5\right)\cdot\frac{1}{49}=7^2\cdot\frac{1}{2}\cdot\frac{1}{49}=49\cdot\frac{1}{49}\cdot\frac{1}{2}=\frac{1}{2}\)

g) \(\frac{4^6\cdot3^5-2^{12}\cdot3^6}{2^{12}\cdot9^3+8^4\cdot3^5}=\frac{\left(2^2\right)^6\cdot3^5-2^{12}\cdot3^6}{2^{12}\cdot\left(3^2\right)^3+\left(2^3\right)^4\cdot3^5}\)

\(=\frac{2^{12}\cdot3^5-2^{12}\cdot3^6}{2^{12}\cdot3^6+2^{12}\cdot3^5}=\frac{2^{12}\left(3^5-3^6\right)}{2^{12}\left(3^6+3^5\right)}=\frac{2^{12}\left[3^5\left(1-3\right)\right]}{2^{12}\left[3^5\left(3+1\right)\right]}=\frac{2^{12}\cdot3^5\cdot\left(-2\right)}{2^{12}\cdot3^5\cdot4}=\frac{-2}{4}=-\frac{1}{2}\)

                                                               Bài giải

\(f,\text{ }\left(1\text{ : }\frac{1}{7}\right)^2\left[\left(2^2\right)^3\text{ : }2^5\right]\cdot\frac{1}{49}\)

\(=7^2\left(2^6\text{ : }2^5\right)\cdot\frac{1}{7^2}\)

\(=2\)

\(g,\text{ }\frac{4^6\cdot3^5-2^{12}\cdot3^6}{2^{12}\cdot9^3+8^4\cdot3^5}=\frac{2^{12}\cdot3^5-2^{12}\cdot3^6}{2^{12}\cdot3^6+2^{12}\cdot3^5}=\frac{2^{12}\cdot3^5\cdot\left(1-3\right)}{2^{12}\cdot3^5\cdot\left(3+1\right)}=-\frac{2}{4}=-\frac{1}{2}\)

 \(A=\frac{1}{\left(x+1\right)\left(x+3\right)}+\frac{1}{\left(x+3\right)\left(x+5\right)}+\frac{1}{\left(x+5\right)\left(x+7\right)}+\frac{1}{\left(x+7\right)\left(x+9\right)}+\frac{1}{\left(x+9\right)\left(x+11\right)}\)

\(=\frac{1+1+1+1+1}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)\left(x+9\right)\left(x+11\right)}\)

\(=\frac{5}{\left(x+1\right)\left(x+3\right)\left(x+5\right)\left(x+7\right)\left(x+9\right)\left(x+11\right)}\)

\(=\frac{5}{\left(x+1\right)\left(x+11\right)\left(x+3\right)\left(x+9\right)\left(x+5\right)\left(x+7\right)}\)

\(=\frac{5}{\left(x^2+11x+x+11\right)\left(x^2+9x+3x+27\right)\left(x^2+7x+5x+35\right)}\)

\(=\frac{5}{\left(x^2+12x+11\right)\left(x^2+12x+27\right)\left(x^2+12x+35\right)}\)

A=\(\frac{1}{x+1}-\frac{1}{x+3}+\frac{1}{x+3}-\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+7}+\frac{1}{x+7}-\frac{1}{x+9}+\frac{1}{x+9}-\frac{1}{x+11}\)

Rút gọn hết đi ta có \(\frac{1}{x+1}-\frac{1}{x+11}\)=\(\frac{x+11}{\left(x+1\right).\left(x+11\right)}-\frac{x+1}{\left(x+1\right).\left(x+11\right)}\)

A=\(\frac{x+11-x-1}{\left(x+1\right).\left(x+11\right)}\)

A=\(\frac{10}{x^2+12x+11}\)

\(A=\frac{1}{\left(x+1\right)\left(x+3\right)}+\frac{1}{\left(x+3\right)\left(x+5\right)}+\frac{1}{\left(x+5\right)\left(x+7\right)}+\frac{1}{\left(x+7\right)\left(x+9\right)}+\frac{1}{\left(x+9\right)\left(x+11\right)}\)

\(A=\frac{1}{x+1}-\frac{1}{x+3}+\frac{1}{x+3}-\frac{1}{x+5}+...+\frac{1}{x+9}-\frac{1}{x+11}\)

\(A=\frac{1}{x+1}-\frac{1}{x+11}\Leftrightarrow A=\frac{x+11}{\left(x+1\right)\left(x+11\right)}+\frac{x+1}{\left(x+1\right)\left(x+11\right)}\)

\(\Leftrightarrow A=\frac{2x+12}{\left(x+1\right)\left(x+11\right)}\)