11)11) 3x(x-5)²-(x+2)³+2(x-1)³-(2x+1)(4x²-2x+1)=3x(x²-10x+25)-(x³+6x²+12x+8)+2(x³-3x²+3x-1)-(8x³+1)=3x³-30x²+75x-x³-6x²-12x-8+2x³-6x²+6x-2-8x³-1=-4x³-42x²+63x-11

nhìn khó thế

câu 63: A

câu 64: B

câu 65: C

mấy câu còn lại phải từ từ đã!

Câu 63: A

Câu 64: B

Câu 65: C

Câu 71: D

Câu 72: A

Câu 73: C

Câu 74: B

Câu 75: C

Câu 76: B

Câu 77: A

Câu 78: C

Câu 79: B

Câu 80: C

\(\Leftrightarrow sin\left(2x+\dfrac{\pi}{3}\right)=\dfrac{1}{2}\)

\(\Leftrightarrow\left[{}\begin{matrix}2x+\dfrac{\pi}{3}=\dfrac{\pi}{6}+k2\pi\\2x+\dfrac{\pi}{3}=\dfrac{5\pi}{6}+k2\pi\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{\pi}{12}+k\pi\\x=\dfrac{\pi}{4}+k\pi\end{matrix}\right.\)

Nghiệm dương nhỏ nhất là \(x=\dfrac{\pi}{4}\approx0.79\)

Đáp án C

a)

\(n_{H_2}=\dfrac{5}{22,4}\left(mol\right)\)

PTHH: 2Na + 2H₂O --> 2NaOH + H₂

          \(\dfrac{5}{11,2}\)<-------------------\(\dfrac{5}{22,4}\)

=> \(m_{Na}=\dfrac{5}{11,2}.23=\dfrac{575}{56}\left(g\right)\)

b) 

PTHH: 2H₂ + O₂ --t^o--> 2H₂O

Xét \(\dfrac{V_{O_2}}{V_{H_2}}=\dfrac{n_{O_2}}{n_{H_2}}=\dfrac{1}{2}\)

=> \(V_{O_2}=\dfrac{1}{2}.5=2,5\left(l\right)\)

\(PTHH:2Na+2H_2O\underrightarrow{t^o}2NaOH+H_2\)

              0,1       0,1         0,1        0,2

\(n_{H_{2_{ }}}=\dfrac{V}{22,4}=\dfrac{5}{22,4}=0,2\left(mol\right)\)

m_Na=n.M=0,1.23=2,3(g)

PTHH: 2H₂+O₂\(\underrightarrow{t^o}\)2H₂O

             0,1   0,05

\(V_{O_2}\)=n.22,4=0,05.22,4=1,12l

\(a,3x-3y=3\left(x-y\right)\\ b,4x^2y-2xy^2+6xy=2xy\left(2x-y+3\right)\\ c,10ab-5a^2=5a\left(2b-a\right)\\ d,3\left(x+y\right)+y\left(x+y\right)=\left(x+y\right)\left(3+y\right)\\ e,x^2-y^2+3x+3y=\left(x-y\right)\left(x+y\right)+3\left(x+y\right)=\left(x+y\right)\left(x-y+3\right)\\ f,ab-a-2b+2=a\left(b-1\right)-2\left(b-1\right)=\left(a-2\right)\left(b-1\right)\)

\(g,x^2+2xy+y^2-16=\left(x+y\right)^2-4^2=\left(x+y+4\right)\left(x+y-4\right)\\ h,a^2-b^2+2a+1=\left(a^2+2a+1\right)-b^2=\left(a+1\right)^2-b^2=\left(a+b+1\right)\left(a-b+1\right)\\ i,x^3+4x^2+4=x\left(x^2+4x+4\right)=x\left(x+2\right)^2\)

Ex1 ko có verb à

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