\(=4.\left(-\dfrac{1}{8}\right)-2.\dfrac{1}{4}-\dfrac{3}{2}+1=\)

\(=-\dfrac{1}{2}-\dfrac{1}{2}-\dfrac{3}{2}+1=-\dfrac{3}{2}\)

= 4 . -1/8 - 2 . -1/4 + 3 . -1/2 + 1

= -1/2 - -1/2 + -3/2 + 1

= -1/2

\(\dfrac{1}{5}:\left(x-3\right)+\dfrac{1}{2}=1\dfrac{1}{8}\\ \Rightarrow\dfrac{1}{5}:\left(x-3\right)=\dfrac{9}{8}-\dfrac{1}{2}\\ \Rightarrow\dfrac{1}{5}:\left(x-3\right)=\dfrac{9}{8}-\dfrac{4}{8}\\ \Rightarrow\dfrac{1}{5}:\left(x-3\right)=\dfrac{5}{8}\\ \Rightarrow x-3=\dfrac{1}{5}:\dfrac{5}{8}\\ \Rightarrow x-3=\dfrac{8}{25}\\ \Rightarrow x=\dfrac{8}{25}+3\\ \Rightarrow x=\dfrac{83}{25}\)

\(\dfrac{1}{5}:\left(x-3\right)+\dfrac{1}{2}=1\dfrac{1}{8}\)

\(\dfrac{1}{5}:\left(x-3\right)+\dfrac{1}{2}=\dfrac{9}{8}\)

\(\dfrac{1}{5}:\left(x-3\right)=\dfrac{9}{8}-\dfrac{1}{2}=\dfrac{9}{8}-\dfrac{4}{8}\)

\(\dfrac{1}{5}:\left(x-3\right)=\dfrac{5}{8}\)

\(x-3=\dfrac{1}{5}:\dfrac{5}{8}=\dfrac{1}{5}.\dfrac{8}{5}\)

\(x-3=\dfrac{8}{25}\)

\(x=\dfrac{8}{25}+3=\dfrac{8}{25}+\dfrac{75}{25}\)

\(x=\dfrac{83}{25}\)

Nghiệm của đa thức trên là: x = 9

Ngiệm là 9 nha

Bạn xem lại đề bài

\(\dfrac{a}{b}=\dfrac{c}{d}\Rightarrow\dfrac{2a}{2b}=\dfrac{3c}{3d}=\dfrac{2a+3c}{2b+3d}=\dfrac{2a-3c}{2b-3d}\)

\(\Rightarrow\dfrac{2a+3c}{2a-3c}=\dfrac{2b+3d}{2b-3d}\)

\(\Rightarrow dpcm\)

\(\dfrac{y}{5}=\dfrac{z}{6}\Rightarrow z=\dfrac{5y}{6}\)

mà \(z-y=40\)

\(\Rightarrow\dfrac{5y}{6}-y=40\)

\(\Rightarrow-\dfrac{y}{6}=40\)

\(\Rightarrow y=-240\Rightarrow z=40+y=40-240=-200\)

\(\dfrac{x}{3}=\dfrac{y}{4}\Rightarrow x=\dfrac{3y}{4}=\dfrac{3.\left(-240\right)}{4}=-180\)

Vậy \(\left\{{}\begin{matrix}x=-180\\y=-240\\z=-200\end{matrix}\right.\)

\(S=\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+...+\dfrac{1}{78.79.80}\)

\(\Rightarrow S=\dfrac{79\left(79+3\right)}{4\left(79+1\right)\left(79+2\right)}\)

\(S=\dfrac{79.82}{4.80.81}=\dfrac{79.41}{160.81}=\dfrac{3239}{12960}\)

\(\text{2.24.25+3.31.16+6.2.8.17}\)

\(=\text{2.6.4.25+3.31.16+6.16.17}\)

\(=\text{12.100+16.3(31+2.17)}\)

\(=\text{1200+48(31+34)}=1200+48.65=1200+3120=4320\)

\(A=\dfrac{1}{3}-\left[\left(-\dfrac{5}{4}\right)-\left(\dfrac{1}{4}+\dfrac{3}{8}\right)\right]\)

\(A=\dfrac{1}{3}-\left[\dfrac{-5}{4}-\dfrac{5}{8}\right]=\dfrac{1}{3}-\left(\dfrac{-15}{8}\right)\)

\(A=\dfrac{53}{24}\)

=> A > 2

=> C là đáp án đúng

A

\(a^2=3b^2\)

Vì \(a^2;b^2\) là số chính phương

\(\Rightarrow a^2⋮̸3b^2\)

Nên không tồn tại a;b nguyên dương thỏa đẳng thức \(a^2=3b^2\)

Phần lỗi màu đỏ là a² không thể chia cho 3 có thương là b² là số chính phương