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(1)3x²-x-4>0(2)x²-x-12≤0(3)x&#1...

(x-2)(x-1)=12 x^2-3x+2=12 x^2-3x-10=0 (x-5)(x+2)=0 x1=5 x2=-2

解:(1)y'=2x3x^2-9x2x+12 =6x^2-18x+12 y''=6x2x-18 =12x-18 令y''=0 12x-18=0 2x-3=0 2x=3 x=3/2 x=3/2.f(3/2)=1/2 答拐点为(3/2,1/2) (2)凹凸性 当x0 f(x)在(3/2,+无穷)上为凹函数 综上:(-无穷,3/2)商是凸函数,(3/2,+无穷)上为凹...

(1)3x2-4x=0,x(3x-4)=0,∴x1=0,x2=43;(2)2(x-3)2-(x+3)(x-3)=0,(x-3)(2x-6-x-3)=0,(x-3)(x-9)=0,∴x1=3,x2=9;(3)x2-12x=4,x2-12x+36=40,(x-6)2=40,x-6=±210,∴x1=6+210,x2=6-210;(4)a=5,b=-8,c=2,△=64...

(1)x3+3x2-4=x3+2x2+x2-4=x2(x+2)+(x+2)(x-2)=(x+2)(x2+x-2)=(x+2)(x+2)(x-1)=(x+2)2(x-1).(2)x4-11x2y2+y4=(x4-2x2y2+y4)-9x2y2=(x2-y2)2-(3xy)2=(x2-y2+3xy)(x2-y2-3xy).(3)x3+9x2+26x+24=(x3+2x2)+...

5-x =(x+2)+(3-2x) 所以|x+2|=x+2 |2x-3|=3-2x 原式=(x-4)√(2x-3)²+(1+2x)√(x+2)² =(x-4)|2x-3|+(1+2x)|x+2| =(x-4)(3-2x)+(1+2x)(x+2) =-2x²+11x-12+2x²+5x+2 =16x-10

3x²-(x+2)²=12 3x²-x²-4x-4=12 2x²-4x-16=0 x²-2x-8=0 (x+2)(x-4)=0 x=-2或x=4

解: (x-1)/3-(y+2)/4=0 ① (x-3)/4-(y-3)/3=1/12 ② 整理得 4x-3y=10 ③ 3x-4y=-2 ④ ③*3-④*4得7y=38 y=38/7 ③*4-④*3得7x=46 x=46/7 解得x=46/7, y=38/7 .

x^4+4x-8 =(x^4-16)+4(x+2) =(x+2)[(x^2+4)(x-2)+4] =(x+2)(x^3-2x^2+4x-4)=0 x=-2,另一个三次方程必须用卡当公式做,你的做法第四行错误,可能是你的方程输入有错误,要么最高次项是x^2,要么第二项是4x^2

4(2x-1)-3(x+2)=2(x-9) 8x-4-3x-6=2x-18 3x=-8 x=-8/3

3(x-4)=2(x+3) 3x-12=2x+6 3x-2x=6+12 x=18

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