10x²-5x+15 = 5(2x²-x+3)
4x²+7x = x(4x+7)
9x²(x+1)+6x(5+x) = 3x[3x(x+1)+2(5+x)]
(11x-3)²+(11x-3)(5+9x) = (11x-3)(11x-3)+(11x-3)(5+9x)
= (11x-3)[(11x-3)+(5+9x)]
= (11x-3)(20x+2)
= 2(11x-3)(10x+1)
t² + 81 + 18t = t² + 18t + 81 = t² + 2*t*9 + 9² = (t+9)²
x² + 36 + 12x = x² + 12x + 36 = x² + 2*x*6 + 6² = (x+6)²
9x²+6x+1 = (3x)² + 2*3x*1 + 1² = (3x+1)²
81+16y²+72y = 16y² + 72y + 81
= (4y)² + 2*4y*9 + 9²
= (4y+9)²
