2720x+136x-1360x-272x=1224
1224x=1224
x=1
Y=(x²+1)∧(-1/2), y'=-1/2*(x²+1)^(-3/2)*2x=-x/√(x²+1)³
1/25a^2+1/10ab+1/16b^2=(1/5a+1/4b)^2; 0,09a^2-4b^2=(0,3a-2b)(0,3a+2b); 16a^2b^2-48abc+36c^2=4(4a^2b^2-12abc+9c^2)=4(2ab-3c)^2; 25x^2+30xy+9y^2=(5x+3y)^2; a^2-6a+9/a-3=(a-3)^2/(a-3)=a-3.