Question

10道题答案

求导

Answer 1

1,3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,其中x=-2,y=-3,z=1, 原式=3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz =3x'y-2x'y+2xyz-x'z+4x'z-xyz =x'y-xyz+3x'z 当x=2,y=3,z=1时原式=4*(-3)-2*3*1+3*4*1 =-12-6+12 =-6 2,3X+2Y)+(4X+3Y)其中X=5,Y+3 原式=3X+2Y+4X+3Y=7X+5Y 当X=5,Y=3时原式=5*7+（-3）*5+20 =35-15+20 =40 3,2x-3(2x-x)+(2y-y),其中x=1,y=2 解；原式=2x-3x+y 当x=1,y=2时原式=2*1-3*1+2 =2-3+2 =1 4,(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),其中a=-1,b=1 =5a^2-3b^2+a^2+b^2-5a^2-3b^2 =a^2-5b^2 =(-1)^2-5*1^2 =1-5 =-4 5,2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2其中a=-2,b=2 =2a^2b+2ab^2-2a^2b+2-2ab^2-2 =0, 6,a^2-ab+2b^2=3 求2ab-2a^2-4b^2-7的值 2ab-2a^2-4b^2-7 =2(ab-a^2-2b^2)-7 =-2(a^2-ab+2b^2)-7 =(-2)*3-7 =-6-7 =-13 7,若A=2x^2+3xy-2x-3,B=-x^2+xy+2,且3A+6B的值与x无关,求y的值 3A+6B=6x^2+9xy-6x-9-6x^2+6xy+12 =15xy-6x+3 =x(15y-6)+3 8,x+6x^2 -3(x-2/3x^2).其中x=-2 9x+6x2 -3(x-2/3x2) =9x+6x2-3x+2x2 =8x2+6x =8×(-2)2+6×(-2) =32-12 =20 9,1/4(-4x^2+2x-8)-(1/2x-1),其中x=1/2 1/4(-4x2+2x-8)-(1/2x-1) =-x2+1/2x-2-1/2x+1 =-x2-1 =-(1/2)2-1 =-1/4-1 =-5/4, 10,3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,其中x=-2,y=-3,z=1, :3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz =3x'y-2x'y+2xyz-x'z+4x'z-xyz =x'y-xyz+3x'z =4*(-3)-2*3*1+3*4*1 =-12-6+12 =-6 11,(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),其中a=-1,b=1 =5a^2-3b^2+a^2+b^2-5a^2-3b^2 =a^2-5b^2 =(-1)^2-5*1^2 =1-5 =-4 12、2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2其中a=-2,b=2 =2a^2b+2ab^2-2a^2b+2-2ab^2-2 =0 13、(X-2分之1Y-1)(X-2分之1Y+1)-(X-2分之1Y-1)的平方,其中X=1.7,Y=3.9 [(X-2分之1Y)-1][(X+2分之1Y)+1]-(X-2分之1Y-1)平方 =(X+2分之1Y)平方-1-(X-2分之1Y)平方+2(X-2分之1Y)-1 =(X+2分之1Y)平方-(X-2分之1Y)平方+2(X-2分之1Y)-2 =2XY+2X-Y-2 =3.9*2.4+1.4 =10.76 14,2a-（3a-2b+2）+（3a-4b-1),其中a=5 b=-3 =2a-3a+2b-2+3a-4b-1 =（2-3+3）a+（2-4）b+（-2-1） =2a-2b-3 =10-(-6)-3 =10+6-3 =13 15,5-(1-x)-1-(x-1）-2x+(-5y）,其中x=2,y=2x =4-2x-5y =4-4-20 =-20 16,2x-(x+3y)-(-x-y)-(x-y),其中x=3,y=-3 =2x-x+3y+x+y-x+y =x+5y =3-15 =-12 17,-ab+3ba-(-2ab),其中a=2,b=1 =-ab+3ba+2ab =2ab+2ab =4ab =4*2*1 =8 18,-m-[-(2m-3n)]+[-(-3m)-4n],其中m=2,n=1 =-m-(-2m+3n)+3m-4n =-m-4m+2m-3n+3m =-3n =-3*1 =-3 19,2（2a+2ab)-2(2ab-1)-2ab-2,其中a=-2 b=2 =4a+4ab-4ab+2-2ab-2 =4a-2ab =4*(-2)-2*(-2)*2 =-8-(-8) =8+8 =0 20,3ab-4ab+8ab-7ab+ab,其中a=-2,b=3 =-8ab+9ab =ab =-2*3 =-6