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x^3%8x^2%9x+72=0,1分钟求出解

(x-1)(x-8)=0 x-1=0,x-8=0 x1=1,x2=8

(x-1)(x-8)=0 x=1 或 x=8

十字交叉法

f(x)=2x³-9x²+12x+8c f'(x)=6x²-18x+12=6(x-1)(x-2) f(x)在(0,1)增 (1,2)减 (2,3)增 有极大值f(1)=5+8c 端点值f(3)=9+8c f(3)>f(1),则9+8c9或c

x^2-4x+3

x²-9x+8=0 (x-1)(x-8)=0 x-1=0或x-8=0 x=1或8

求导,得f'(x)=3x^2-18x+15=3(x^2-6x+5)=3(x-1)(x-5) 令f'(x)>0,解得x5 令f‘(x)

先把括号里的乘出来么 x/9*8+2*8=x 把关于x的移到左边数字的到右边 8x/9-x=-16 (8/9-1)x=-16 -x/9=-16 x=144

简算: 99.9x0.8+11.1x2.8 =11.1x9x0.8+11.1x2.8 =11.1x7.2+11.1x2.8 =11.1x(7.2+2.8) =11.1x10 =111

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