Question

x^2 + 4xy - 21y^2

5x^2 + 6xy + y^2

x^2 + 2xy - 15y^2

(x - y)^2 + 4(x - y) - 12

x^2v- 7xy + 10y^2

x^2yz + 5xyz - 14yz

Answer 1

2) \(5x^2+6xy+y^2\) 

 \(=9x^2+6xy+y^2-4x^2\)  

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

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

 \(=\left(5x+y\right)\left(x+y\right)\) 

3) \(x^2+2xy-15y^2=x^2+2xy+y^2-16y^2\) 

  \(=\left(x+y\right)^2-\left(4y\right)^2\)

  \(=\left(x+y+4y\right)\left(x+y-4y\right)\) 

   \(=\left(x+5y\right)\left(x-3y\right)\) 

hc tốt