close
標題:
初中數學題(20分)
發問:
最佳解答:
1) x/18 = (1/3) - (x/2) x/18 = (2-3x)/6 x = 6 - 9x 10x = 6 x = 3/5 2) (5/3k) + (1/k) = -2 (5-3)/3k = -2 -6k = 8 k = -4/3 3) (1/8) + (2/b) - (1/12)=0 2/b = (1/12) - (1/8) 2/b = -1/24 b = -48 4) (x+8)/x = 6 x + 8 = 6x 5x = 8 x = 8/5 5) (20/c) + c = -9 20 + c2 =-9c c2+9c+20 = 0 (c+4)(c+5) = 0 c = -4 or c = -5 6) [(x+6)/(x+4)] + [1/(x2-x-12)] = 1 [(x+6)/(x+4)] + [1/(x-4)(x+3)] = 1 [(x+6)(x-4)(x+3)/(x+4)(x-4)(x+3)] + [(x+4)/(x+4)(x-4)(x+3)]= 1 (x3+5x2-18x-72+x+4)/(x3+3x2-16x-48) = 1 x3+5x2-17x-68 = x3+3x2-16x-48 2x2-x-20 = 0 x = (1+√161)/4 or x = (1-√161)/4 7) h = 2A/(b+d) 2A = h(b+d) A = h(b+d)/2 8) (5/x) - (4/y) = (5/z) 5/x = (5/z) +(4/y) 5/x = (5y+4z)/yz x/5 = yz/(5y+4z) x = 5yz/(5y+4z) 9) P/n = rt P = nrt 10) (1/a) +(1/b) = 1 (1/a) = 1 - (1/b) (1/a) = (b-1)/b a = b/(b-1) 11) F = (L2/6d) + (d/2) L2/6d = F- (d/2) L2/6d =(2F-d)/2 L2 =3d(2F-d) 12) (1/7) - (1/a) = (a/7a) - (7/7a) = (a-7)/7a 13) [(2t+2)/(t2+2t+1)] - [1/(t+1)] = [2(t+1)/(t+1)2] - [1/(t+1)] = [2/(t+1)] - [1/(t+1)] = 1/(t+1) 14) [6/(b-1)] - [b/(1-b)] = [6/(b-1)] + [b/(b-1)] = (b+6)/(b-1) 15) [(n+7)/(n+3)] - [(n-3)/(n+7)] = [(n+7)2/(n+3)(n+7)] - [(n+3)(n-3)/(n+3)(n+7)] = (n2+14n+49-n2+9)/(n+3)(n+7) = (14n+58)/(n+3)(n+7) = 2(7n+29)/(n+3)(n+7) 16) [6/(a2-9)] - [5/(a2-a-6)] = [6/(a+3)(a-3)] - [5/(a+2)(a-3)] = [6(a+2)/(a+2)(a+3)(a-3)] - [5(a+3)/(a+2)(a+3)(a-3)] = (6a+12-5a-15)/(a+2)(a+3)(a-3) = (a-3)/(a+2)(a+3)(a-3) = 1/(a+2)(a+3) 17) [x/(x-1)] + (1/x) = [x2/x(x-1)] + [(x-1)/x(x-1)] = (x2+x-1)/x(x-1) 18) [(x+2)/2x] - [(2-x)/x2] = [x(x+2)/2x2] - [2(2-x)/2x2] = [(x2+2x-4+2x)/2x2] = (x2+4x-4)/2x2 19) (8/c) + 6 = (8/c) + (6c/c) = (6c+8)/c 20) [4/(t+2)] -[7/(t+2)2] = [4(t+2)/(t+2)2] - [7/(t+2)2] = (4t+8-7)/(t+2)2 = (4t+1)/(t+2)2 21) [2/(3y-6)] + [3/(4y+8)] = [2/3(y-2)] + [3/4(y+2)] = [8(y+2)/12(y+2)(y-2)] + [9(y-2)/12(y+2)(y-2)] = (8y+16+9y-18)/12(y+2)(y-2) = (17y-2)/12(y+2)(y-2)
其他解答:
初中數學題(20分)
發問:
此文章來自奇摩知識+如有不便請留言告知
Rational Expressions and Equations.1) x/18=1/3 -x/2 2) 5/3k + 1/k=-23) 1/8 + 2/b - 1/12=04) x+8/x=65) 20/c +c=-96) x+6/x+4 + 1/x^2 -x-12=17) h= 2A/b+d for A8) 5/x - 4/y= 5/z for x9) P/n =rt for P10) 1/a+1/b= 1 for a11) F= L^2/6d + d/2 for L^212) 1/7 -1/a13) 2t+2/ t^2 +2t+1 - 1/t+114)... 顯示更多 Rational Expressions and Equations. 1) x/18=1/3 -x/2 2) 5/3k + 1/k=-2 3) 1/8 + 2/b - 1/12=0 4) x+8/x=6 5) 20/c +c=-9 6) x+6/x+4 + 1/x^2 -x-12=1 7) h= 2A/b+d for A 8) 5/x - 4/y= 5/z for x 9) P/n =rt for P 10) 1/a+1/b= 1 for a 11) F= L^2/6d + d/2 for L^2 12) 1/7 -1/a 13) 2t+2/ t^2 +2t+1 - 1/t+1 14) 6/b-1 - b/1-b 15) n+7/n+3 - n-3/n+7 16) 6/a^2 -9 - 5/a^2 -a-6 17) x/x-1 +1/x 18) x+2/2x - 2-x/x^2 19) 8/c +6 20) 4/t+2 -7/(t+2)^2 21) 2/3y-6 + 3/4y+8最佳解答:
1) x/18 = (1/3) - (x/2) x/18 = (2-3x)/6 x = 6 - 9x 10x = 6 x = 3/5 2) (5/3k) + (1/k) = -2 (5-3)/3k = -2 -6k = 8 k = -4/3 3) (1/8) + (2/b) - (1/12)=0 2/b = (1/12) - (1/8) 2/b = -1/24 b = -48 4) (x+8)/x = 6 x + 8 = 6x 5x = 8 x = 8/5 5) (20/c) + c = -9 20 + c2 =-9c c2+9c+20 = 0 (c+4)(c+5) = 0 c = -4 or c = -5 6) [(x+6)/(x+4)] + [1/(x2-x-12)] = 1 [(x+6)/(x+4)] + [1/(x-4)(x+3)] = 1 [(x+6)(x-4)(x+3)/(x+4)(x-4)(x+3)] + [(x+4)/(x+4)(x-4)(x+3)]= 1 (x3+5x2-18x-72+x+4)/(x3+3x2-16x-48) = 1 x3+5x2-17x-68 = x3+3x2-16x-48 2x2-x-20 = 0 x = (1+√161)/4 or x = (1-√161)/4 7) h = 2A/(b+d) 2A = h(b+d) A = h(b+d)/2 8) (5/x) - (4/y) = (5/z) 5/x = (5/z) +(4/y) 5/x = (5y+4z)/yz x/5 = yz/(5y+4z) x = 5yz/(5y+4z) 9) P/n = rt P = nrt 10) (1/a) +(1/b) = 1 (1/a) = 1 - (1/b) (1/a) = (b-1)/b a = b/(b-1) 11) F = (L2/6d) + (d/2) L2/6d = F- (d/2) L2/6d =(2F-d)/2 L2 =3d(2F-d) 12) (1/7) - (1/a) = (a/7a) - (7/7a) = (a-7)/7a 13) [(2t+2)/(t2+2t+1)] - [1/(t+1)] = [2(t+1)/(t+1)2] - [1/(t+1)] = [2/(t+1)] - [1/(t+1)] = 1/(t+1) 14) [6/(b-1)] - [b/(1-b)] = [6/(b-1)] + [b/(b-1)] = (b+6)/(b-1) 15) [(n+7)/(n+3)] - [(n-3)/(n+7)] = [(n+7)2/(n+3)(n+7)] - [(n+3)(n-3)/(n+3)(n+7)] = (n2+14n+49-n2+9)/(n+3)(n+7) = (14n+58)/(n+3)(n+7) = 2(7n+29)/(n+3)(n+7) 16) [6/(a2-9)] - [5/(a2-a-6)] = [6/(a+3)(a-3)] - [5/(a+2)(a-3)] = [6(a+2)/(a+2)(a+3)(a-3)] - [5(a+3)/(a+2)(a+3)(a-3)] = (6a+12-5a-15)/(a+2)(a+3)(a-3) = (a-3)/(a+2)(a+3)(a-3) = 1/(a+2)(a+3) 17) [x/(x-1)] + (1/x) = [x2/x(x-1)] + [(x-1)/x(x-1)] = (x2+x-1)/x(x-1) 18) [(x+2)/2x] - [(2-x)/x2] = [x(x+2)/2x2] - [2(2-x)/2x2] = [(x2+2x-4+2x)/2x2] = (x2+4x-4)/2x2 19) (8/c) + 6 = (8/c) + (6c/c) = (6c+8)/c 20) [4/(t+2)] -[7/(t+2)2] = [4(t+2)/(t+2)2] - [7/(t+2)2] = (4t+8-7)/(t+2)2 = (4t+1)/(t+2)2 21) [2/(3y-6)] + [3/(4y+8)] = [2/3(y-2)] + [3/4(y+2)] = [8(y+2)/12(y+2)(y-2)] + [9(y-2)/12(y+2)(y-2)] = (8y+16+9y-18)/12(y+2)(y-2) = (17y-2)/12(y+2)(y-2)
其他解答:
文章標籤
全站熱搜
留言列表
