T(t+7)–4t–28=0
t^2+7t–4t–28=0
t^2+3t–28=0
a=1
b=3
c=–28
D=3^2–4*1*(–28)=9+112=121
^D=11
x1=–3+11/2=8/2=4
x2=–3–11/2=–14/2=–7
(u+s)(u-s)+(s+d)(s-d)=u²-s²+s²-d²=u²-d²=(u-d)(u+d)
<span>(3b+3)(-2b+2)-2b(-3b-2)=-6b^2-6b+6b+6+6b^2+4b=4b+6</span>
А)у^2+6у-6у=у
Б)с^2-4с+4-3с^2+4с=-2с^2+4