1.) 8x^2+(4.5-x^2)-(5.4x^2-1)=8x^2+4.5-x^2-5.4x^2+1=1,6х^2+5,5
2.) (a^2-5ab)-(7-3ab)+(2ab-a^2)=a^2-5ab-7+3ab+2ab-a^2=-7
1.) 8x^2+(4.5-x^2)-(5.4x^2-1)=8x^2+4.5-x^2-5.4x^2+1=1,6х^2+5,5
2.) (a^2-5ab)-(7-3ab)+(2ab-a^2)=a^2-5ab-7+3ab+2ab-a^2=-7