bài14: viết số thập phân thích hợp vào chỗ chấm 

4m 25cm =  4,25  m

12m 8dm= 12,8  m

26m 8cm =  26,08 m

248 dm =  24,8 m

36 dm =  3,6  m

a) \(\left(x-1\right)^2=0\)

\(\Rightarrow x-1=0\)

\(\Rightarrow x=1\)

b) \(\left(x-3\right)^2=1\)

\(\Rightarrow\left(x-3\right)^2=1^2\)

\(\Rightarrow\left[{}\begin{matrix}x-3=-1\\x-3=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x=4\end{matrix}\right.\)

\(\dfrac{x}{\dfrac{4}{2}}=\dfrac{4}{\dfrac{x}{2}}\)

\(\Rightarrow\dfrac{x}{2}=\dfrac{8}{x}\)

\(\Rightarrow x^2=8\cdot2\)

\(\Rightarrow x^2=16\)

\(\Rightarrow x^2=4^2\)

\(\Rightarrow\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

a) \(\dfrac{11}{3}-\dfrac{2}{3}\times\dfrac{5}{6}\)

\(=\dfrac{11}{3}-\dfrac{10}{18}\)

\(=\dfrac{11}{3}-\dfrac{5}{9}\)

\(=\dfrac{33}{9}-\dfrac{5}{9}\)

\(=\dfrac{28}{9}\)

b) \(\dfrac{13}{2}+\dfrac{7}{6}:\dfrac{2}{3}\)

\(=\dfrac{13}{2}+\dfrac{7}{6}\cdot\dfrac{3}{2}\)

\(=\dfrac{13}{2}+\dfrac{7}{4}\)

\(=\dfrac{26}{4}+\dfrac{7}{4}\)

\(=\dfrac{33}{4}\)

c) \(\dfrac{28}{9}-\dfrac{3}{4}+\dfrac{1}{3}\)

\(=\dfrac{28}{9}+\dfrac{3}{9}-\dfrac{3}{4}\)

\(=\dfrac{31}{9}-\dfrac{3}{4}\)

\(=\dfrac{124}{36}-\dfrac{27}{36}\)

\(=\dfrac{97}{36}\)

d) \(\dfrac{5}{8}:\dfrac{2}{3}\times\dfrac{1}{5}\)

\(=\dfrac{5}{8}\times\dfrac{3}{2}\times\dfrac{1}{5}\)

\(=\dfrac{15}{80}\)

\(=\dfrac{3}{16}\)

\(2,023\times570+2,023\times575-145\times2,023\)

\(=2,023\times\left(570+575-145\right)\)

\(=2,023\times1000\)

\(=2023\)

\(P\left(x\right)=-2x^4-7x+\dfrac{1}{2}-6x^4+2x^2-x\)

\(P\left(x\right)=\left(-2x^4-6x^4\right)-\left(7x+x\right)+2x^2+\dfrac{1}{2}\)

\(P\left(x\right)=-8x^4-8x+2x^2+\dfrac{1}{2}\)

______

\(Q\left(x\right)=3x^3-x^4-5x^2+x^3-6x+\dfrac{3}{4}\)

\(Q\left(x\right)=\left(3x^3+x^3\right)-x^4-5x^2-6x+\dfrac{3}{4}\)

\(Q\left(x\right)=4x^3-x^4-5x^2-6x+\dfrac{3}{4}\)

a) \(f\left(x\right)+g\left(x\right)+h\left(x\right)\)

\(=6x^7-5x^3+1-3+2x-4x^7-2x^7+2x+7x^2\)

\(=-5x^3+7x^2+4x-2\)

b) \(f\left(x\right)+g\left(x\right)-h\left(x\right)\)

\(=6x^7-5x^3+1-3+2x-4x^7-\left(-2x^7+2x+7x^2\right)\)

\(=2x^7-5x^3+2x-2+2x^7-2x-7x^2\)

\(=4x^7-5x^3-7x^2-2\)

200000000 + 70000000 + 50000 + 40 = ..270050040.....

x + x + x + x + x + x + x = .7x...

a . 100000 + b . 1000 + 6 = ...100000a+1000b+6........

....3457890120000+21... = 3457890120021

a) \(\left(25\times32\right):8\)

\(=25\times32:8\)

\(=25\times4\)

\(=100\)

b) \(24\times11+6\times86\times4+72\)

\(=24\times11+24\times86+24\times3\)

\(=24\times\left(11+86+3\right)\)

\(=24\times100\)

\(=2400\)

c) \(36\times5+9\times79\times4+72\times8\)

\(=36\times5+36\times79+36\times2\times8\)

\(=36\times\left(5+79+16\right)\)

\(=36\times100\)

\(=3600\)

d) \(\left(56\times125\right):7\)

\(=56:7\times125\)

\(=8\times125\)

\(=1000\)

\(129-5\left[29\left(6-1^2\right)\right]\)

\(=129-5\left[29\left(6-1\right)\right]\)

\(=129-5\left(29\cdot5\right)\)

\(=129-5\cdot145\)

\(=129-725\)

\(=-596\)