Question

Cho x+y =1 tính giá trị của m=8x2 + 16x2y + 16xy2 + 8y2- 5x - 5y + 2018

Answer 1

thay x=1 y=1 ta được m

Answer 2

\(8x^2+16x^2y+16xy^2+8y^2-5x-5y+2018\)

\(=8\left(x^2+y^2\right)+16xy\left(x+y\right)-5\left(x+y\right)+2018\)

\(=8\left[\left(x+y\right)^2-2xy\right]+16xy\left(x+y\right)-5\left(x+y\right)+2018\)  

\(=8\left(x+y\right)^2-16xy+16xy\left(x+y\right)-5\left(x+y\right)+2018\)

\(=8\left(x+y\right)^2-16xy\left[1-\left(x+y\right)\right]-5\left(x+y\right)+2018\)

\(=8.1^2-16xy\left(1-1\right)-5.1+2018\)

\(=8-0-5+2018\)

\(=2021\)

!!!Chúc học tốt!!!