1+1=?
2x2=?
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\(\left(2x^2+1\right)\left(4x-3\right)=\left(2x^2+1\right)\left(x-13\right)\)
\(\Leftrightarrow\left(2x^2+1\right)\left(4x-3-x+13\right)=0\)
\(\Leftrightarrow\left(2x^2+1\right)\left(3x+10\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x^2+1=0\\3x+10=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2=-\dfrac{1}{2}\left(VN\right)\\x=-\dfrac{10}{3}\end{matrix}\right.\)
\(S=\left\{-\dfrac{10}{3}\right\}\)
\(\left(2x^2+1\right)\left(4x-3\right)=\left(2x^2+1\right)\left(x-12\right)\)
\(\Leftrightarrow\left(2x^2+1\right)\left(4x-3\right)-\left(2x^2+1\right)\left(x-12\right)=0\)
\(\Leftrightarrow\left(2x^2+1\right)\left(4x-3-x+12\right)=0\)
\(\Leftrightarrow\left(2x^2+1\right)\left(3x+9\right)=0\)
\(\Leftrightarrow3x+9=0\) (do \(2x^2+1>0\forall x\in R\))
\(\Leftrightarrow x=-3\)
-Vậy \(S=\left\{-3\right\}\)
H(-1) = 2\(x^2\)- 10
H(-1) = 2.(-1)2 - 10
H(-1) = 2 - 10
H(-1) = -8
H(\(\dfrac{1}{2}\)) = 2\(x^2\) - 10
H(\(\dfrac{1}{2}\)) = 2.(\(\dfrac{1}{2}\))2 - 10
H(\(\dfrac{1}{2}\)) = \(\dfrac{1}{2}\) - 10
H(\(\dfrac{1}{2}\)) = \(-\dfrac{19}{2}\)
a) \(M=\frac{2\times2}{1\times5}+\frac{2\times2}{5\times9}+\frac{2\times2}{9\times13}+...+\frac{2\times2}{45\times40}\)
\(M=\frac{4}{1\times5}+\frac{4}{5\times9}+\frac{4}{9\times13}+...+\frac{4}{45\times49}\)
\(M=1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{45}-\frac{1}{49}\)
\(M=1-\frac{1}{49}\)
\(M=\frac{48}{49}\)
b) \(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...+\frac{1}{1+2+3+4+5+...+10}\)
= \(\frac{2}{2\times\left(1+2\right)}+\frac{2}{2\times\left(1+2+3\right)}+...+\frac{2}{2\times\left(1+2+3+...+10\right)}\)
\(=\frac{2}{6}+\frac{2}{12}+...+\frac{2}{110}\)
\(=\frac{2}{2\times3}+\frac{2}{3\times4}+...+\frac{2}{10\times11}\)
\(=2\times\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\right)\)
\(=2\times\left(\frac{1}{2}-\frac{1}{11}\right)\)
\(=2\times\frac{9}{22}\)
\(=\frac{9}{11}\)
Mình trả lời câu a nha M= 4/1*5+4/5*9+4/9*13+...+4/45*49 M=1-1/5+1/5-1/9+1/9-1/13+...+1/45-1/49 M=1-1/49=48/49
A = − 6 x 5 + 4 x 4 + 2 x 3 − 2 x 2 + 2 x 3 − 6 x 2 + 2 x
A = − 6 x 5 + 4 x 4 + 4 x 3 − 8 x 2 + 2 x
Chọn đáp án C
\(P\left(-1\right)=\left(-1\right)^4+2.\left(-1\right)^2+1=4\\ P\left(1\right)=1^4+2.1^2+1=4\)
\(P\left(-1\right)=\left(-1\right)^4+2\cdot\left(-1\right)^2+1=4\)
\(P\left(1\right)=P\left(-1\right)=4\)
\(Q\left(2\right)=2^4+4\cdot2^3+2\cdot2^2-4\cdot2+1=49\)
\(Q\left(1\right)=1^4+4\cdot1^3+2\cdot1^2-4\cdot1+1=4\)
1+1=2
2nhân2=4
1+1=2
2x2=4
là tiếng anh lớp 7 dữ chx