Question

去括号并化简过程详细

(9a^2-12ab+5b^2)-2(7a^2-6ab+5b^2)

(-5x^3-x^2)-(-7x^3+2x^2)
3x-[5x-4(2x-1)]
-3(a^2-bc+b^2)-2(-a^2+bc-2b^2)

Answer 1

(9a^2-12ab+5b^2)-2(7a^2-6ab+5b^2)
=9a^2-12ab+5b^2-14a^2+12ab-10b^2
=(9a^2-14a^2)-(12ab-12ab)+(5b^2-10b^2)
=-5a^2-5b^2

(-5x^3-x^2)-(-7x^3+2x^2)
=-5x^3-x^2+7x^3-2x^2
=(-5x^3+7x^3)-(x^2+2x^2)
=2x^3-3x^2

3x-[5x-4(2x-1)]
=3x-[5x-8x+4]
=3x+3x-4
=6x-4

-3(a^2-bc+b^2)-2(-a^2+bc-2b^2)
=-3a^2+3bc-3b^2+2a^2-2bc+4b^2
=(-3a^2+2a^2)+(3bc-2bc)-(3b^2-4b^2)
=-a^2+bc+b^2