Question

(x-2y-z) ^2
need a perfect way to solve this...
please help.​

Answer 1

Answer:

x²+4y²+z²-4xy+4yz-2xz

Step-by-step explanation:

(x-2y-z)²

= x²+(-2y)²+(-z)²+2*x*(-2y)+2*(-2y)*(-z)+2*(-z)*x

= x²+4y²+z²-4xy+4yz-2xz

using formula

(x+y+z)² = x²+y²+z²+2xy+2yz+2xz

Answer 2

Formula:

(a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ac

∴ (x - 2y - z)²

= (x)² + (- 2y)² + (- z)² + 2(x)(- 2y) + 2(- 2y)(- z) + 2(- z)(x)

= x² + 4y² + z² - 4xy + 4yz - 2xz

More formulae:

• (x + a)(x + b) = x² + (a + b)x + ab
• (a ± b)³ = a³ ± b³ ± 3ab(a ± b)
• a³ + b³ + c³ - 3abc = (a + b + c)(a² + b² + c² - ab - bc - ca)