Câu hỏi của Sakura Sakura

Question

Cho x-y=7.Tính:

1)A=x(x+2)+y(y-2)-2xy+37

2)$B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-9^5$

Mặc Chinh Vũ · Accepted Answer

$A=x\left(x+2\right)+y\left(y-2\right)-2xy+37$

$A=x^2+2x+y^2-2y-2xy+37$

$A=\left(x^2+y^2-2xy+1+2x-2y\right)+36$

$A=\left(x-y+1\right)^2+36$

$A=\left(7+1\right)^2+36$

$A=8^2+36$

$A=100$Câu trả lời: $A=x\left(x+2\right)+y\left(y-2\right)-2xy+37$

$A=x^2+2x+y^2-2y-2xy+37$

$A=\left(x^2+y^2-2xy+1+2x-2y\right)+36$

$A=\left(x-y+1\right)^2+36$

$A=\left(7+1\right)^2+36$

$A=8^2+36$

$A=100$

Mặc Chinh Vũ · Answer

$B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95$ $(9^5$ $sai$$)$

$B=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95$

$B=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+xy-3xy+y^2\right)-95$

$B=\left(x-y\right)^3+\left(x^2-2xy+y^2\right)-95$

$B=\left(x-y\right)^3+\left(x-y\right)^2-95$

$B=7^3+7^2-95$

$B=297$Câu trả lời: $B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95$ $(9^5$ $sai$$)$

$B=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95$

$B=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+xy-3xy+y^2\right)-95$

$B=\left(x-y\right)^3+\left(x^2-2xy+y^2\right)-95$

$B=\left(x-y\right)^3+\left(x-y\right)^2-95$

$B=7^3+7^2-95$

$B=297$

Bài 5: Những hằng đẳng thức đáng nhớ (Tiếp)