\(a,16x^2+24xy+.....\)
\(=\left(4x\right)^2+2.4x.3y+\left(3y\right)^2\)
\(=\left(4x+3y\right)^2\)
Vậy \(....=9y^2\)
\(b,25x^2+....+81\)
\(=\left(5x\right)^2+....+9^2\)
\(=\left(5x\right)^2+2.5x.9+9^2\)
\(=\left(5x+9\right)^2\)
Vậy \(....=90x\)
\(c,....-42xy+49y^2\)
\(=49y^2-42xy+....\)
\(=\left(7y\right)^2-2.7y.3x+\left(3x\right)^2\)
\(=\left(7y-3x\right)^2\)
\(=\left(3x-7y\right)^2\)
Vậy \(....=9x^2\)
Đúng 1
Bình luận (0)
