Khai triển theo hằng đẳng thức
a. (1/x - 5 ) ( 1/x + 5 )
b ( x/3 - y/4 ) ( x/3 + y/4 )
d. ( x/y - 2/3 ) ( x/y + 2/3 )
e ( 2x - 2/3 ) ( 2/3 + 2x )
g . ( 2x + 3/5 ) ( 3/5 -2x )
h, ( 1/2 x - 4/3 ) ( 4/3 + 1/2x )
i. ( 2/3x^2 - Y/2 ) 9 2/3X^2 + Y/2 )
a; (\(\dfrac{1}{x}\) - 5)(\(\dfrac{1}{x}\) + 5)
= (\(\dfrac{1}{x}\))2 - 52
= \(\dfrac{1}{x^2}\) - 25
b; (\(\dfrac{x}{3}\) - \(\dfrac{y}{4}\))(\(\dfrac{x}{3}\) + \(\dfrac{y}{4}\))
= \(\left(\dfrac{x}{3}\right)^2\) - \(\left(\dfrac{y}{4}\right)^2\)
= \(\dfrac{x^2}{9}\) - \(\dfrac{y^2}{16}\)
d; (\(\dfrac{x}{y}\) - \(\dfrac{2}{3}\) (\(\dfrac{x}{y}\)+\(\dfrac{2}{3}\))
= (\(\dfrac{x}{y}\))2 - (\(\dfrac{2}{3}\))2
= \(\dfrac{x^2}{y^2}\) - \(\dfrac{4}{9}\)
e; (2\(x\) - \(\dfrac{2}{3}\))(\(\dfrac{2}{3}\) + 2\(x\))
= (2\(x\))2 - (\(\dfrac{2}{3}\))2
= 4\(x^2\) - \(\dfrac{4}{9}\)