Bài 1: Viết biểu thức sau dưới dạng tổng 2 bình phương
a) x\(^2\)+10x +26 + y\(^2\)+ 2y
b) x\(^2\)- 2xy + 2y\(^2\)+ 2y + 1
c) 4x\(^2\)+ 2z\(^2\)- 4xz - 2z + 1
Bài 2: Tính nhanh
a) 127\(^2\)+146 . 127 + 73\(^2\)
b) 31,8\(^2\)- 63,6 . 21,8 + 21,8\(^2\)
c) 2018\(^2\)- 2017\(^2\)+ 2016\(^2\)-2015\(^2\)+...+2\(^2\)-1
d) 2017\(^2\)- 2016 . 2018
Bài 1:
a, \(x^2+10x+26+y^2+2y\)
\(=x^2+2.x.5+5^2+y^2+2.y.1+1^2\)
\(=\left(x+5\right)^2+\left(y+1\right)^2\)
b, \(x^2-2xy+2y^2+2y+1\)
\(=x^2-2.x.y+y^2+y^2+2.y.1+1^2\)
\(=\left(x-y\right)^2+\left(y+1\right)^2\)
c, \(4x^2+2z^2-4xz-2z+1\)
\(=\left(2x\right)^2-2.2x.z+z^2+z^2-2.z.1+1^2\)
\(=\left(2x-z\right)^2+\left(z-1\right)^2\)
Chúc bạn học tốt!!!
Bài1:
Bn kia giải r nhé
Bài 2:
a)\(127^2+146.127+73^2=127^2+2.73.127+73^2\)
=\(\left(127+73\right)^2=200^2=40000\)
b)\(31,8^2-63,6.21,8+21,8^2=\left(31,8-21,8\right)^2=10^2=100\)
c)\(2018^2-2017^2+2016^2-2015^2+...+2^2-1\)
=\(\left(2018+2017\right)+\left(2015+2016\right)+...+\left(2+1\right)\)
=4025+4031+...+3
=...(bn tự tính)
d)\(2017^2-2016.2018=2017^2-\left(2017^2-1\right)=1\)
