Question

[Hà Thu]

  chi ttết ạ cảm ơn nhiều

Answer 1

[Nguyễn Lê Phước Thịnh]

c: \(25-a^2+2ab-b^2\)

\(=25-\left(a^2-2ab+b^2\right)\)

\(=5^2-\left(a-b\right)^2\)

\(=\left(5-a+b\right)\left(5+a-b\right)\)

d: \(\dfrac{1}{27}a^3y-8b^3y\)

\(=y\left(\dfrac{1}{27}a^3-8b^3\right)\)

\(=y\left[\left(\dfrac{1}{3}a\right)^3-\left(2b\right)^3\right]\)

\(=y\left(\dfrac{1}{3}a-2b\right)\left[\left(\dfrac{1}{3}a\right)^2+\dfrac{1}{3}a\cdot2b+\left(2b\right)^2\right]\)

\(=y\left(\dfrac{1}{3}a-2b\right)\left(\dfrac{1}{9}a^2+\dfrac{2}{3}ab+4b^2\right)\)

e: \(a^3-a+b^3-b\)

\(=\left(a^3+b^3\right)-\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2-ab+b^2\right)-\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2-ab+b^2-1\right)\)

g: \(5x^4y^2+20x^3y^2+20x^2y^2\)

\(=5x^2y^2\cdot x^2+5x^2y^2\cdot4x+5x^2y^2\cdot4\)

\(=5x^2y^2\left(x^2+4x+4\right)=5x^2y^2\left(x+2\right)^2\)