а) x^2+2x
прибавь один: x^2+2x+1=(x+1)^2
б)<span> a²+4ab</span>
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<span>прибавь 4b^2: <span> a²+4ab+4b^2=(a+2b)^2</span></span>
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<span><span>в) <span>m² +1</span></span></span>
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<span><span><span>прибавь 2m: <span>m² +1 +2m=(m+1)^2</span></span></span></span>
1)(m-3n)/8n(m+n) -(m+3n)/8n(m-n)=[(m-3n)(m-n)-(m+3n)(m+n)[/8n(m-n)(m+n)=
=(m²-mn-3mn+3n²-m²-mn-3mn-3n²)/8n(m-n)(m+n)=-8mn/8n(m-n)(m+n)==n/(n-m)
2)x²-x+1 - x³/(x+1)=(x³+x²-x²-x+x+1-x³)/(x+1)=1/(x+1)
3)(3c+7)/c(c+7) +(c-7)/7(c+7)=(21c+49+c²-7c)/7c(c+7)=(c²+14c+49)/7c(c+7)=(c+7)²/7c(c+7)=(c+7)/7c
Надеюсь это тебе поможет)