1 - 1/cos^2a = (cos^2a-1)/cos^2a= -sin^2a/cos^2a= -tg^2a
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{y+2z=14
{y=z-4
z-4+2z=14
3z=18
z=6
y=6-4=2
{x-y=4
{xy=12
{x=4+y
{xy=12
(4+y)*y=12
4y+y²-12=0
y=-6 Або у=2 (т-ма Вієта)
x=4-6=-2 Або х=4+2=6
(5а+6)^2 -81=(5а)²+2*5а*6+6²-81=25а²+60а+36-81=25а²+60а-45
25-(а+7)^2 =25-(а²+2*а*7+7²)=25-(а²+14а+49)=25-а²-14а-49=-а²-14а-24
9m^2-(1+2m)^2=9м²-1-4м-4м²=5м²-4м-1
(5x-3y)^2 -16x^2=25х²-30ху+9у²-16х²=9х²-30ху+9у²
(5c-3d)^2 -9d^2=25с²-30сд+9д²-9д²=25с-30сд
49m^2-(n+8m)^2=49м<span>²-н²-16нм+64м²=113м²-16нм-н²</span>
A)7.42*5.9+11.48:9.5\0.35=(43.778+1.2)\0.35=44.978\0.35=128.5
б)(-5.17\7.4+1.67*4.7)*(-12.11)=(0.6+7.849)*(-12.11)=8.449*-12.11=102.31