1) x²-6xy+9y² = x²-2*x*3y+(3y)² = (x-3y)²
2) n²+14n+49 = n²+2*n*7+7² = (n+7)²
3) a²+2a+1 = a²+2*a*1+1² = (a+1)²
4) b²-12bc+36c² = b²-2*b*6c+(6c)² = (b-6c)²
1) x²-6xy+9y² = x²-2*x*3y+(3y)² = (x-3y)²
2) n²+14n+49 = n²+2*n*7+7² = (n+7)²
3) a²+2a+1 = a²+2*a*1+1² = (a+1)²
4) b²-12bc+36c² = b²-2*b*6c+(6c)² = (b-6c)²