Question

B1: Tính giá trị các biểu thức sau

a) A = (\(-x^3\)\(y^3\))\(^4\) : (\(-x^{12}\)\(y^{11}\)) tại x= \(\dfrac{3}{4}\);y = \(\dfrac{-4}{3}\)

b) B = 25(\(x^2\)\(y^4\))\(^2\) : 15\(x^4\)\(y^6\) tại x = 2017; y = \(\dfrac{3}{5}\)

Answer 1

a: \(A=\dfrac{\left(-x^3y^3\right)^4}{-x^{12}y^{11}}=\dfrac{x^{12}y^{12}}{-x^{12}y^{11}}=-y\)

Khi y=-4/3 thì \(A=-\left(-\dfrac{4}{3}\right)=\dfrac{4}{3}\)

b: \(B=25\left(x^2y^4\right)^2:15x^4y^6\)

\(=\dfrac{25}{15}\cdot\dfrac{x^4}{x^4}\cdot\dfrac{y^8}{y^6}=\dfrac{5}{3}y^2\)

Khi y=3/5 thì \(B=\dfrac{5}{3}\cdot\left(\dfrac{3}{5}\right)^2=\dfrac{5}{3}\cdot\dfrac{9}{25}=\dfrac{45}{75}=\dfrac{3}{5}\)