3-0,9x+1-X-0,6=-0,2
-X=-0,2-3-1+0,6
-X=-3,6
X=3,6
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) 4х=21
х=21/4
2)4х=-12
х=-3
3)х=6
4)х=-11