tính tổng
S=(-9\(a^2\))\(\frac{1}{3}b\)+a2 +24a \(\left(-\frac{1}{4}ab\right)\)
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a)\(=x^3.\left(2+\frac{3}{5}x^2\right)\)(đặt nhân tử chung)
b)\(=\left(7a^2-5a\right).\left(a+5\right)\)\(=a\left(7a-5\right).\left(a+5\right)\)
c)\(=6ab\left(2a-3b+4ab\right)\)
d)\(=a.\left(a-b\right)-\left(7a-7b\right)\)
\(=a.\left(a-b\right)-7\left(a-b\right)\)
\(=\left(a-7\right).\left(a-b\right)\)
e) \(=\left(\frac{1}{2}a^2b+\frac{1}{4}ab\right)+\frac{1}{2}\left(a+\frac{1}{2}\right)\)
\(=\frac{1}{2}ab\left(a+\frac{1}{2}\right)+\frac{1}{2}\left(a+\frac{1}{2}\right)\)
\(=\left(\frac{1}{2}ab+\frac{1}{2}\right).\left(a+\frac{1}{2}\right)\)
Có gì không đúng bạn thông cảm cho mình nhớ =))
Phân tích đa thức thành nhân tử bằng phương pháp đặt nhân tử chung
\(a^3c+a^2bc-a^2b^2-abc^2\)
Bài 1:
Ta có:
\(\left(a-b+c\right)^3=a^3-b^3+c^3-3a^2b+3a^2c+3ab^2+3b^2c+3ac^2-3bc^2-6abc\)
\(\Rightarrow\left(\sqrt[3]{\frac{1}{9}}-\sqrt[3]{\frac{2}{9}}+\sqrt[3]{\frac{4}{9}}\right)^3=\frac{1}{9}-\frac{2}{9}+\frac{4}{9}-\frac{1}{3}.\sqrt[3]{2}+\frac{1}{3}.\sqrt[3]{4}+\frac{1}{3}.\sqrt[3]{4}+\frac{2}{3}.\sqrt[3]{2}\)
\(+\frac{2}{3}.\sqrt[3]{2}-\frac{2}{3}.\sqrt[3]{4}-\frac{4}{3}=\sqrt[3]{2}-1\)
\(\Rightarrow\sqrt[3]{\sqrt[3]{2}-1}=\sqrt[3]{\frac{1}{9}}-\sqrt[3]{\frac{2}{9}}+\sqrt[3]{\frac{4}{9}}\)
\(\left(\frac{-2}{3}+\frac{3}{7}\right):\frac{4}{5}+\left(\frac{-1}{3}+\frac{4}{7}\right):\frac{4}{5}\)
\(=\left(\frac{-2}{3}+\frac{3}{7}+\frac{-1}{3}+\frac{4}{7}\right):\frac{4}{5}\)
\(=\left[\left(\frac{-2}{3}+\frac{-1}{3}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)\right]:\frac{4}{5}\)
\(=\left[\left(-1+1\right)\right]:\frac{4}{5}\)
\(=0:\frac{4}{5}=0\)
~ Hok tốt ~
x. (x^2)^3 = x^5
x^7 ≠ x^5
Nếu,
x^7 - x^5 = 0
mủ lẻ nên phương trình có 3 nghiệm
Đáp số:
x = -1
hoặc
x = 0
hoặc
x = 1
a, \(\left(1-\frac{1}{4}\right)\cdot\left(1-\frac{1}{9}\right)\cdot\left(1-\frac{1}{16}\right)\cdot\left(1-\frac{1}{25}\right)\cdot\left(1-\frac{1}{36}\right)\)
\(=\frac{3}{4}\cdot\frac{8}{9}\cdot\frac{15}{16}\cdot\frac{24}{25}\cdot\frac{35}{36}\)
\(=\frac{1.3}{2.2}\cdot\frac{2.4}{3.3}\cdot\frac{3.5}{4.4}\cdot\frac{4.6}{5.5}\cdot\frac{5.7}{6.6}\)
\(=\frac{1.2.3.4.5}{2.3.4.5.6}\cdot\frac{3.4.5.6.7}{2.3.4.5.6}=\frac{1}{6}\cdot\frac{7}{2}\)
\(=\frac{7}{12}\)
b, \(\left(2-\frac{3}{2}\right)\cdot\left(2-\frac{4}{3}\right)\cdot\left(2-\frac{5}{4}\right)\cdot\left(2-\frac{6}{5}\right)\)
\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}=\frac{1.2.3.4}{2.3.4.5}\)
\(=\frac{1}{5}\)
c) C = ( 1 - 2 ) + ( 3 - 4 ) + ... + ( 79 - 80 )
C = ( -1 ) + ( -1 ) + ... + ( -1 )
C = ( -1 ) x ( 80 - 1 + 1 ) : 2
C = ( -1 ) x 80 : 2
C = ( -40 )
Ta có:
\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)........\left(1-\frac{1}{2017}\right).\left(1-\frac{1}{2018}\right)\)
\(\Rightarrow B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{2016}{2017}.\frac{2017}{2018}\)
Đởn giản hết sẽ còn là:
\(\Rightarrow B=\frac{1}{2018}\)
\(S=\left(-9a^2\right).\dfrac{1}{3}b+a^2+24a\left(-\dfrac{1}{4}ab\right)\\ =\left[\left(-9\right).\dfrac{1}{3}\right]a^2b+a^2+\left[24.\left(-\dfrac{1}{4}\right)\right]\left(a.a\right)b\\ =-3a^2b+a^2+\left(-6\right)a^2b\\ =-9a^2b+a^2\)