先去括号,在合并同类项 ①-(x+y)+(3x-7y) ②2a+2(a+1)-3(a-1) ③4a^2-3a+3-3(-a^3+2a^2+1)

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先去括号,在合并同类项 ①-(x+y)+(3x-7y) ②2a+2(a+1)-3(a-1) ③4a^2-3a+3-3(-a^3+2a^2+1)
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先去括号,在合并同类项 ①-(x+y)+(3x-7y) ②2a+2(a+1)-3(a-1) ③4a^2-3a+3-3(-a^3+2a^2+1)
先去括号,在合并同类项 ①-(x+y)+(3x-7y) ②2a+2(a+1)-3(a-1) ③4a^2-3a+3-3(-a^3+2a^2+1)

先去括号,在合并同类项 ①-(x+y)+(3x-7y) ②2a+2(a+1)-3(a-1) ③4a^2-3a+3-3(-a^3+2a^2+1)
①-(x+y)+(3x-7y)
=-x-y+3x-7y=2x-8y
②2a+2(a+1)-3(a-1)
=2a+2a+2-3a+3=a+5
③4a^2-3a+3-3(-a^3+2a^2+1)
=4a^2-3a+3+3a^3-6a^2-3
=3a^3-2a^2-3a
=a(3a^2-2a-3)

(1)原式=- x-y+3x-7y=2x-8y (2)原式=2a+2a+2-3a+3=a+5
(3)原式=4a^2-3a+3+3a^3-6a^2-3=+3a^3-2a^2-3a