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\(\left(2x+1\right)\left(x+3\right)+\left(x+1\right)^2\left(x+2\right)+\left(x+5\right)\left(x+1\right)\)
\(=2x^2+6x+x+3+x^3+2x^2+x+2x^2+4x+2+x^2+x+5x+5\)
\(=x^3+7x^2+18x+10\)
đúng ko nhỉ?
tham khảo : KHAI TRIỂN RÚT GỌN ĐA THỨC BẰNG CASIO (1LINK DUY NHẤT) - YouTube
\(a.\left(2xy-3\right)^2=4x^2y^2-12xy+9\)
\(b.\left(\dfrac{1}{2}x+\dfrac{1}{3}\right)^2=\dfrac{1}{4}x^2+\dfrac{1}{3}x+\dfrac{1}{9}\)
a: \(=-\left[\left(\dfrac{1}{3}ab^2+2a^3b\right)^3\right]\)
\(=\dfrac{-1}{27}a^3b^6-3\cdot\dfrac{1}{9}a^2b^4\cdot2a^3b-3\cdot\dfrac{1}{3}ab^2\cdot4a^6b^2-8a^9b^3\)
\(=\dfrac{-1}{27}a^3b^6-\dfrac{2}{3}a^5b^5-4a^7b^4-8a^9b^3\)
b: \(=x^3+3x^2+3x+1-x^3+3x^2-3x+1-6\left(x^2-1\right)\)
\(=6x^2+2-6x^2+6\)
=8
\(\left(3x^2-2y\right)^3=27x^6-54x^4y+36x^2y^2-8y^3\)
a) \(\left(\dfrac{x^2}{2}+y^2\right)^2\)
\(=\left(\dfrac{1}{2}x^2+y^2\right)^2\)
\(=\left(\dfrac{1}{2}x^2\right)^2+2\cdot\dfrac{1}{2}x^2\cdot y^2+\left(y^2\right)^2\)
\(=\dfrac{1}{4}x^4+x^2y^2+y^4\)
b) \(\left(\dfrac{4}{5}x^2-\dfrac{2}{3}y\right)^2\)
\(=\left(\dfrac{4}{5}x^2\right)^2-2\cdot\dfrac{4}{5}x^2\cdot\dfrac{2}{3}y+\left(\dfrac{2}{3}y\right)^2\)
\(=\dfrac{16}{25}x^4-\dfrac{16}{15}x^2y+\dfrac{4}{9}y^2\)
c) \(\left(2x+\dfrac{1}{2}\right)\left(2x-\dfrac{1}{2}\right)\)
\(=\left(2x\right)^2-\left(\dfrac{1}{2}\right)^2\)
\(=4x^2-\dfrac{1}{4}\)
a: (1/2x^2+y^2)^2
=(1/2x^2)^2+2*1/2x^2*y^2+y^4
=1/4x^4+x^2y^2+y^4
b: (4/5x^2-2/3y)^2
=(4/5x^2)^2-2*4/5x^2*2/3y+4/9y^2
=16/25x^4-16/15x^2y+4/9y^2
c: =(2x)^2-(1/2)^2
=4x^2-1/4
\(=3x^2\left(x^2-1\right)+\left(x^8-3x^4+3x^2-1\right)-\left(x^8-1\right)\)
\(=3x^4-3x^2+x^8-3x^4+3x^2+1-x^8+1\)
\(=2\)
=2 nha ban
(con cach lam ban nhan dang thuc len rui rut gon lai)
a)
\(\begin{array}{l}{\left( {{x^2} + 2y} \right)^3} = {\left( {{x^2}} \right)^3} + 3.{\left( {{x^2}} \right)^2}.2y + 3.{x^2}.{\left( {2y} \right)^2} + {\left( {2y} \right)^3}\\ = {x^6} + 6{x^4}y + 12{x^2}{y^2} + 8{y^3}\end{array}\)
b)
\({\left( {\dfrac{1}{2}x - 1} \right)^3} = {\left( {\dfrac{1}{2}x} \right)^3} - 3.{\left( {\dfrac{1}{2}x} \right)^2}.1 + 3.\dfrac{1}{2}x{.1^2} - {1^3} = \dfrac{1}{8}{x^3} - \dfrac{3}{4}{x^2} + \dfrac{3}{2}x - 1\)
\(\left(2a^2+1\right)^3=\left(2a^2+1\right)\left(2a^2+1\right)\left(2a^2+1\right)\\ =\left(4a^4+4a^2+1\right)\left(2a^2+1\right)\\ =8a^6+8a^4+2a^2+4a^4+4a^2+1\\ =8a^6+12a^4+6a^2+1\)
\(\left(2a^2+1\right)^3=8a^6+12.a^4+6a^2+1\)