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(1)解方程组:x+2y=?13x?2y=9;(2)先化简,...

(1)原式=-9y+6x2+3y-2x2=-6y+4x2,当x=2,y=-1时,原式=6+16=22;(2)方程去分母得:8x-4-6x+9=12,移项合并得:2x=7,解得:x=72.

(1)原式=(a+1a+1-1a+1)÷a(a?1)a+1=aa+1×a+1a(a?1)=1a?1,当a=12时,原式=112?1=-2;(2)x+y=7①3x+y=17②,②-①得,2x=10,解得x=5;把x=5代入①得,5+y=7,解得y=2,故此不等式组的解集为:x=5y=2.

(1)(x+3)2+(x+2)(x-2)-2x2,=x2+6x+9+x2-4-2x2,=6x+5.当x=?13时,原式=6×(-13)+5,=3.(2)x?1x?2-1x?2=3,∴x?2x?2=3.∴x-2=3x-6,∴x=2,检验:把x=2代入分母得0.∴x=2是增根,∴原分式方程无解.

(1)原式=(x2y2-4-2x2y2+4)÷xy=(-x2y2)÷xy=-xy,当x=10,y=125时,原式=-10×125=-25;(2)去分母得:(x+1)2-4=x2-1,整理得:x2+2x+1-4=x2-1,移项合并得:2x=2,解得:x=1,经检验x=1是增根,分式方程无解.

(1)方程两边都乘(x+1)(x-1)得:x+1+2x(x-1)=2(x+1)(x-1)化简合并得:x=3经检验x=3是原方程的根.(2)原式=2(a+3)(a?2)2×a?2a(a+3)?1a?2=2?aa(a?2)=-1a.当a=12时,原式=-2.

1、两边乘以(x+2)(x-2)得 2x-4+2=3x+6 -x=8 ∴x=-8 检验:x=-8是方程的解 2、 x=根号3+根号2/根号3-根号2,y=根号3-根号2/根号3+根号2 ∴xy=1 x=5+2√6 y=5-2√6 ∴x+y=10 x-y=4√6 x³-xy²/x四次方y+2x³y²+x²y³ =x(x+y)...

6x-2(1-x)=x+2-66x-2+2x=x-47x=-2X=-27;(2)原式=10a2-14ab+18b2-42a2+6ab-9b2=-32a2-8ab+9b2当a=34,b=?23时,原式=-32×(316)2-8×34÷(?23)=-18+4+4=-10.

(1)原方程变为:(x?12)2=34(2分)∴x1=1+32,x2=1?32.(4分)(用求根公式法解答可参照给分)解:(2)原式=x+1?2(x?2)x2?4×x+2x?5(1分)=12?x(3分)将x=2+2代入得,原式=12?(2+2)=?22.(4分)

(1)方程两边同时乘以x-2得,1+3(x-2)=x-1,解得x=2,当x=2时,x-2=2-2=0,故x=2是原分式方程的增根,原分式方程无解;(2)原式=[a+1a?2+11?a]÷a+1a?2=a+1a?2×a?2a+1+11?a×a?2a+1=1+a+21?a2当a=3时,原式=1+3+21?9=38(a≠±1,0,2).

(1)方程两边同乘以(x+1)(x-1)得,2(x+1)=4,解得x=1,检验:x=1时,(x+1)(x-1)=0,故x=1是分式方程的增根,原分式方程无解;(2)原式=x+1?x+1(x+1)(x?1)×2(x+1)(x?1)x=4x,∵x+1≠0且x-1≠0且x≠0,∴x≠±1,0.当x=12时,原式=412=8.

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