<span>a^2-3ab+2b^2/<span>(a-b)^2= a^2-2ab-ab+b^2+b^2/<span>(a-b)^2 = (a^2-2ab+b^2)-(ab-b^2)/<span>(a-b)^2</span></span></span></span>
102k-4k=1960
98k=1960
k=1960:98
k=20