1. с^2 (a+c-b) - d (a+c-b)= (c^2-d)(a+c-b)
<span>11,3у - (9,7у - 0,8у) + 7,4 = 17</span>
<span>11,3у</span>-8,9у=17-7,4
2,4у=9,6
y=9,6/2,4
y=4
:D