Question

2. Hãy biểu diễn đa thức 3x-y dưới dạng mẫu số lần lượt là:

a)7; b)x; c) 9x+y; d)3x-y;

Answer 1

a)\(3x-y\) = \(\dfrac{7\left(3x-y\right)}{7}=\dfrac{21x-7y}{7}\)

b) \(3x-y=\dfrac{\left(3x-y\right)x}{x}=\dfrac{3x^2-xy}{x}\)

c) \(3x-y=\dfrac{\left(3x-y\right)\left(9x+y\right)}{9x+y}\)

d) \(3x-y=\dfrac{\left(3x-y\right)\left(3x-y\right)}{3x-y}=\dfrac{\left(3x-y\right)^2}{3x-y}\)

Answer 2

a) 3x - y = \(\dfrac{7\left(3x-y\right)}{7}=\dfrac{21x-7y}{7}\)

Answer 3

3x-y=\(\dfrac{7\cdot\left(3x-y\right)}{7}\) =\(\dfrac{21x-7y}{7}\)

3x-y=\(\dfrac{x\cdot\left(3x-y\right)}{x}\) =\(\dfrac{3x^2-xy}{x}\)