F(x)=(cos3x)/3
F´(x)=(1/3).3.(-sin3x)=-sin3x
2a(3a - 5) - (a - 3) (a- 7) =
= 6a^2 - 10a - (a^2 - 10a + 21) =
= 6a^2 - 10a - a^2 + 10a - 21 =
= 5a^2 - 21
<span>(y+1)(x-1)=xy+1+y
x=4(y-x)-x
</span><span>
x=4y-4x-x
x=4y-5x
6x=4y
<u>y=1.5x</u>
</span><span><span>(y+1)(x-1)=xy+1+y</span>
(1.5x+1)(x-1)=x*1.5x+1+1.5x *2
(3x+2)(x-1)=3x²+2+3x
<u>3x²</u>-3x+2x-2=<u>3x²</u>+3x+2
-x-2=3x+2
4x=-4
x=-1
y=-1.5
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