Question

[Đỗ Thị Thu Hương]

1 . Phan tich da thuc thanh nhan tu :

x^2 + 6x - 9 -y^2

2. Tim x :

x^2 -x - 12 = 0

Answer 1

[Lightning Farron]

Bài 1:

\(x^2-6x+9-y^2\)

\(=\left(x-3\right)^2-y^2\)

\(=\left(x-3+y\right)\left(x-3-y\right)\)

Bài 2:

\(x^2-x-12=0\)

\(\Leftrightarrow x^2-4x+3x-12=0\)

\(\Leftrightarrow x\left(x-4\right)+3\left(x-4\right)=0\)

\(\Leftrightarrow\left(x+3\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x+3=0\\x-4=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=-3\\x=4\end{array}\right.\)

Answer 2

[Ngọc Nguyễn Minh]

1. x²+6x-9-y²

=-(x²-6x+y²)-3²

=-(x-y)²-3²

=(-x+y-3)(-x+y+3)