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2014-09-25T13:34:02+03:00
3(x+5)-5(1-x)(1+x)=(x+3)^2+(2x-1)^2+13
3x+15-5(1+x-x-x^2)=(x^2+6x+9) + (4x^2-4x+1) +13
3x+15-5(1-x^2)=5x^2+2x+23
3x+15-5+5x^2=5x^2+2x+23
3x+15-5+5x^2-5x^2-2x-23=0x=23+5-15x=13