\(x^2-y^2+z^2-t^2-2xz+2yt\)

\(=\left(x^2+z^2-2xz\right)-\left(y^2+t^2-2yt\right)\)

\(=\left(x-z\right)^2-\left(y-t\right)^2\)

\(=\left(x-z-y+t\right)\left(x-z+y-t\right)\)

x²-y²+z²-t²-2xz+2yt

=(x²-2xz+z²)+(-y²+2yt-t²)

=(x²-2xz+z²)-(y²-2yt+t²)

=(x-z)²-(y-t)²

=(x-z-y+t)(x-z+y-t)

Bạn sửa lại đề bài câu 2) nhé ^^

2) \(a+b+c+d=0\Leftrightarrow a+b=-c-d\Leftrightarrow\left(a+b\right)^3=-\left(c+d\right)^3\)

\(\Leftrightarrow a^3+b^3+3ab\left(a+b\right)=-\left[c^3+d^3+3cd\left(c+d\right)\right]\)

\(\Leftrightarrow a^3+b^3+c^3+d^3=-3cd\left(c+d\right)-3ab\left(a+b\right)\)

\(\Leftrightarrow a^3+b^3+c^3+d^3=3ab\left(c+d\right)-3cd\left(c+d\right)\)

\(\Leftrightarrow a^3+b^3+c^3+d^3=3\left(c+d\right)\left(ab-cd\right)\)

đề đúng ak bạn

99.100 = 9900

(20.1)² = 20² = 400

73² - 27² = (73 - 27).(73 + 27) = 46.100 = 4600

Ủng hộ mk nha ^_-

99,100=9900

(20,1) \(^2\)=20\(^2\) =400

73\(^2\) -27\(^2\) =(73-27),(73+27)=46,100=4600

ủng hộ giùm nha ^^

c) \(-\frac{x^4}{4}+2x^2y^3-4y^6=-\left(\frac{x^4}{4}-2x^2y^3+4y^6\right)=-\left[\left(\frac{x^2}{2}\right)^2-2.\frac{x^2}{2}.2y^3+\left(2y^3\right)^2\right]=-\left(\frac{x^2}{2}-2y^3\right)\)

tích rồi mình mới trả lời

tl đẫ êkk mk 10+ cho na@@