60!/((60-2)!*2!)=60*59*58!/58!*2=30*59=1770
1) <span>(2x-5)^2-x^2=(2х-5-х)(2х-5+х)=(х-5)(3х-5)</span>
<span>2) <span>(5x-2)^2-(x-1)^2=(5х-2-х+1)(5х-2+х-1)=(4х-1)(6х-3)</span></span>
<span><span>3)<span>(3x+2)^2-x^2=(3х+2-х)(3х+2+х)=(2х+2)(4х+2)</span></span></span>
(a+2)./(a+2)ˇ2 -4a/=(a+2)./aˇ2+4a+4-4a/=(a+2).(aˇ2+4)