Question

thực hiện phép tính:

a/(5x-y)²

b/(2x+y²)3

c/(x+\(\dfrac{1}{4}\))²

d/(\(\dfrac{2}{3}\)x²-\(\dfrac{1}{2}\)y)³

Answer 1

a) (5x-y)² = (5x)² - 2.5x.y + y² = 25x² - 10xy +y²

b) (2x + y² )³ = (2x)³ - 3.(2x)².y² + 3.2x.(y²)² - (y²)³ = 8x³ - 12x²y² + 6xy⁴ - y⁶

c) (x + \(\dfrac{1}{4}\))² = x² + 2.x.\(\dfrac{1}{4}\) + (\(\dfrac{1}{4}\))² = x² + \(\dfrac{1}{2}\).x + \(\dfrac{1}{16}\)

d) (\(\dfrac{2}{3}\)x² - \(\dfrac{1}{2}\)y)³ = (\(\dfrac{2}{3}\)x²)³ - 3.(\(\dfrac{2}{3}\)x²)². \(\dfrac{1}{2}\)y + 3.\(\dfrac{2}{3}\)x². ( \(\dfrac{1}{2}\)y)² - (\(\dfrac{1}{2}\)y)³

^{= \(\dfrac{8}{27}\)}x⁶ - \(\dfrac{2}{3}\)x⁴y + \(\dfrac{1}{2}\)x²y² - \(\dfrac{1}{8}\)y³