(<span>a+b)*(a-2b)+(2b-a)*(2b+a)=-(a+b)*(2b-a)+(2b-a)*(2b+a)=(2b-a)(-a-b+2b+a)=(2b-a)b </span>
{х+3y=2
{2х+3y=7
{x=2-3y
[2(-3y+2)+3y-7=0
Решаем вспомогательное ур-ие:
2(-3y+2)+3y-7=0
-6y+4+3y-7=0
-3y=3
y=-1
{x=2+3=5
[y=-1
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<span>1) f(x)=sinx-cosx </span>
<span><span>f'(x)=(sinx)' - (cosx)' = cosx - (-sinx) = cosx + sinx </span></span>
<span><span><span>2) f(x)=tgx-4ctgx</span></span></span>
<span>3) f(x)=4x-sinx </span>
<span>f'(x)=(4x)' - (sinx)' = 4 - cosx</span>
<span> <span>4) f(x)=6cosx-1,2x</span></span>
<span><span><span>f'(x)=(6cosx)' - (1,2x)' = -6sinx-1.2</span></span></span>