(x-5)²+(2x-5)(2x+5)+39x= x²-10x+25+4x²-25+39x=5x²+29x
a1=10, d=3. Sn=2a1 + d(n-1)/2 * n = 20 + 3( 30 - 1) / 2 * 30 = 1605
S(k-1) = 20 + 3* 14/2 * 15 = 465
S(k-n)=Sn - Sk-1
Sk-n= 1605 - 465=1140
dy/dx=sin3x*y
(dy/dx)/y=sin3x
<span>\int{1/y}\, dy = <span>\int{sin3x}\, dx</span></span>
<span><span>logy = (-1/3)*cos3x + C1</span></span>
<span><span>y = e^((-1/3)*cos3x + C1)</span></span>
y = C1*e^((-1/3)*cos3x
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