Question

Phân tích thành nhân tử: x²-7x+9

Answer 1

x²-2.\(\dfrac{7}{2}x+\dfrac{49}{4}-\dfrac{49}{4}+9\)

=\(\left(x^2-2.\dfrac{7}{2}x+\dfrac{49}{4}\right)-\dfrac{13}{4}\)

=\(\left(x-\dfrac{7}{2}\right)^2-\dfrac{13}{4}\)

=\(\left(x-\dfrac{7}{2}-\dfrac{\sqrt{13}}{2}\right)\left(x-\dfrac{7}{2}+\dfrac{\sqrt{13}}{2}\right)\)

=\(\left(x-\dfrac{7+\sqrt{13}}{2}\right)\left(x-\dfrac{7-\sqrt{13}}{2}\right)\)

Answer 2

= x^2 - 6x - x +9

= ( x^2 - 6x +9 ) - x

= ( x - 3)^2 -x