把下列二次函数配方f（x）=3+5x-2x² - 知识问答

把下列二次函数配方f（x）=3+5x-2x²

3个回答

f(x)=-2x²+5x+3
=-2(x²-5x/2)+3
=-2(x²-5x/2+25/16-25/16)+3
=-2(x²-5x/2+25/16)+2×25/16+3
=-2(x-5/4)²+49/8
f(x)=3/4*x²-2x
=(3/4)(x²-8x/3)
=(3/4)(x²-8x/3+16/9-16/9)
=(3/4)(x²-8x/3+16/9)-(3/4)(16/9)
=(3/4)(x-4/3)²-4/3

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