Tính giá trị của biểu thức:
a) A = 8^10 + 4^10
8^4 + 4^11
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\(A=\frac{2^{30}+2^{20}}{2^{12}+2^{22}}=\frac{2^{12}.\left(2^{18}+2^8\right)}{2^{12}.\left(1+2^{10}\right)}=\frac{2^8.\left(2^{10}+1\right)}{1+2^{10}}=2^8\)
Ta có :\(\frac{8^{10}+4^{10}}{8^4+4^{11}}\)=\(\frac{2^{30}+2^{20}}{2^{12}+2^{22}}\)= \(\frac{2^{10}.\left(2^{10}+1\right)}{2^{12}.\left(2^{10}+1\right)}\)=\(\frac{2^{10}}{2^{12}}\)= 4.
a) \(\dfrac{5}{3}+\dfrac{4}{9}:\dfrac{1}{2}=\dfrac{5}{3}+\dfrac{4}{9}\times2=\dfrac{5}{3}+\dfrac{8}{9}=\dfrac{23}{9}\)
b) \(\dfrac{11}{10}-\dfrac{2}{5}:\dfrac{2}{3}=\dfrac{11}{10}-\dfrac{2}{5}\times\dfrac{3}{2}=\dfrac{11}{10}-\dfrac{3}{5}=\dfrac{11}{10}-\dfrac{6}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)
Câu 4
\(\dfrac{12\times15\times20}{10\times16\times25}=\dfrac{3\times4\times3\times5\times4\times5}{5\times2\times4\times4\times5\times5}=\dfrac{3\times3}{5\times2}=\dfrac{9}{10}\)
Câu 3:
\(a.\dfrac{5}{3}+\dfrac{4}{9}:\dfrac{1}{2}=\dfrac{5}{3}+\dfrac{8}{9}=\dfrac{15}{9}+\dfrac{8}{9}=\dfrac{23}{9}\)
\(b.\dfrac{11}{10}-\dfrac{2}{5}:\dfrac{2}{3}=\dfrac{11}{10}-\dfrac{3}{5}=\dfrac{11}{10}-\dfrac{6}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)
Câu 4:
\(\dfrac{12\times15\times20}{10\times16\times25}=\dfrac{3\times3\times1}{2\times1\times5}=\dfrac{9}{10}\)
\(\frac{8^{10}+4^{10}}{8^4+4^{11}}=\frac{2^{30}+2^{20}}{2^{12}+2^{22}}=\frac{2^{20}\left(2^{10}+1\right)}{2^{12}\left(2^{10}+1\right)}=2^8\)
Ta có: \(\frac{8^{10}+4^{10}}{8^4+4^{11}}\)=\(\frac{\left(2^3\right)^{10}+\left(2^2\right)^{10}}{\left(2^3\right)^4+\left(2^2\right)^{11}}\)=\(\frac{2^{30}+2^{20}}{2^{12}+2^{22}}\)=\(\frac{2^{20}.2^{10}+2^{20}}{2^{12}.2^{10}+2^{12}}\)=\(\frac{2^{20}.\left(2^{10}+1\right)}{2^{12}.\left(2^{10}+1\right)}\)=\(\frac{2^{20}}{2^{12}}=2^8\)
\(\frac{8^{10}+4^{10}}{8^4+4^{11}}\)
\(=\frac{\left(2^3\right)^{10}+\left(2^2\right)^{10}}{\left(2^3\right)^4+\left(2^2\right)^{11}}\)
\(=\frac{2^{30}+2^{20}}{2^{12}+2^{22}}\)
\(=\frac{2^{30}+2^{20}}{2^{22}+2^{12}}\)
\(=\frac{2^{20}\left(2^{10}+1\right)}{2^{12}\left(2^{10}+1\right)}\)
\(=\frac{2^{20}}{2^{12}}\)
\(=2^8\)
\(=256\)
`A=sqrt{8+2sqrt7}-sqrt{8-2sqrt7}`
`=sqrt{7+2sqrt7+1}-sqrt{7-2sqrt7+1}`
`=sqrt{(sqrt7+1)^2}-sqrt{(sqrt7-1)^2}`
`=sqrt7+1-sqrt7+1=2`
`B=sqrt{11-6sqrt2}+sqrt{6-4sqrt2}`
`=sqrt{9-2.3.sqrt2+2}+sqrt{4-2.2.sqrt2+2}`
`=sqrt{(3-sqrt2)^2}+sqrt{(2-sqrt2)^2}`
`=3-sqrt2+2-sqrt2=5-2sqrt2`
a) Có x = 2020 => x + 1 = 2021. Thay 2021 = x + 1 vào A
\(A=x^6-\left(x+1\right)^5+\left(x+1\right)x^4-\left(x+1\right)x^3+\left(x+1\right)x^2-\left(x+1\right)x+x+1\)
\(A=x^6-x^6-x^5+x^5+x^4-x^4-x^3+x^3+x^2-x^2-x+x+1\)
\(A=1\)
b) Có x = -19 => x - 1 = -20 => - ( x - 1 ) = 20. Thay 20 = - ( x - 1) vào B
\(B=x^{10}-\left(x-1\right)x^9-\left(x-1\right)x^8-\left(x-1\right)x^7-...-\left(x-1\right)x^2-\left(x-1\right)x-x+1\)
\(B=x^{10}-x^{10}+x^9-x^9+...+x^2-x^2+x-x+1\)
\(B=1\)
Chúc bạn học tốt!!!
A=[ (2^3)^10+(2^2)^10]/[(2^3)^4+(2^2)^11]
=[2^30+2^20]/[2^12+2^22]
=[2^20x(2^10+1)]/[2^12x(1+2^10)]
=2^20/2^12=2^8
XEM LẠI GIÙM MÌNH NHA!
A=8^6 phần 4^1