先因式分解再求值:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)其中x=205 快

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先因式分解再求值:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)其中x=205 快

先因式分解再求值:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)其中x=205 快
先因式分解再求值:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)其中x=205 快

先因式分解再求值:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)其中x=205 快
:(x+3)(x+5)+(5-x)²+(5-x)(2x+7)
=x^2+8x+15+x^2-10x+25-2x^2+3x+35
=x+75
x=205
则 x+75=280

先展开 x^2+8x+15+x^2-10x+25-2x^2+3x+35=x+75=280

(x+3)(x+5)+(5-x)²+(5-x)(2x+7)
=x²+8x+15+25-10x+x²+10x+35-2x²-7x
=x+75
当x=205时, 原式=205+75=280

(x+3)(x+5)+(5-x)²+(5-x)(2x+7)
=(x+3)(x+5)+(x-5)²-(x-5)(2x+7)
=(x+5)(x+3+x-5)-(x-5)(2x+7)
=2(x+5)(x-1)-(x-5)(2x+7)
=2*210*204-200*417

原式=x²+5x+3x+15+25-10x+x²+10x+35-2x²-7x
=x+75
∴=205+75
=280

X^2 +15X+15+25-10X+X^2-2X^2+3X+35
=8X+75
=1715