a.= x^{2} + 1x-x-2+6 x^{2} +15x-2x-5-3 x^{2} -3x= 4 x^{2} +11x-7x
b. = x^{2} +3x-7x-21- x^{2} -2x-x-2+5x-20- x^{2} +4x= x^{2} -2x+43
c. = a^{2}+3ab-ab-3b^{2}+2a^{2}+4ab-ab-2b^{2}-a^{2}+2ab-ab+2ab=2a^{2}+8ab-3b^{2}.
d.2x+2x^{2}-x^{2}-x^{3}-3x^{2}-x^{3}+8+5x+x^{3}+10+2x^{2}=7x-x^{3}+18
X^{2}=x la a doua
X^{3}=x la a treia
a^{2}=a la a doua
2b^{2}= 2b la a doua
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