香港介紹ppt

標題:

• Vitamin C Test
• 巳知長方形的四個頂點分別是A(-1,0),B(2,2),C(0,5)和D(a,b).
• 蝦仔食D咩架-

此文章來自奇摩知識+如有不便請留言告知

F.2 MATH 求恆等式中常數A & B的值

發問:

(8A+3B)x +2B=7x-6 答案:A=2 , B=-3 怎麼計出來呢? 求恆等式中常數A & C的值 2(x^2-1)+Ax=(x+B)(Cx-1)

最佳解答:

(8A+3B)x +2B=7x-6 Since x = unknown, let x = 0, (8A+3B)(0) + 2B = 7(0)-6, (8A+3B)(0) = 0; 7(0) = 0 2B = -6 B = -3 let x = 1 (8A+3B)(1) + 2B =7(1)-6 8A+3(-3) +2(-3) = 1 8A -9-6 = 1 8A = 1+6+9 = 16 A = 2 2(x^2-1)+Ax=(x+B)(Cx-1) let x = 0 2(0^2-1) + A(0) = (0+B)(C(0)-1) 2(-1) + 0 = B (-1) -2 = -B, B = 2 let x = 1 2(1^2-1)+A(1)=(1+2)(C-1) 2(0) + A = 3 (C-1) A = 3C - 3 let x = 2 2(2^2-1)+2A=(2+B)(2C-1) 6 + 2(3C-3) = 4(2C-1) 6+6C-6 = 8C- 4 6C = 8C - 4 4 = 2C C = 2 when C = 2, A = 3C - 3 = 3(2) - 3 A = 3 Check: 2(4-1) + (3)(2) = 4(4-1) = 12

其他解答:

No.1 (8A+3B)x+2B=7x-6 L.H.S.=(8A+3B)x+2B =8Ax+3Bx+2B so, 8Ax+3Bx+2B=7x-6 By Comparing like terms, B=-6/2 =-3 A=(7x-3Bx)/8 =[7x-3*(-3)x]/8 =[7x-(-9)x]/8 =(7x+9x)/8 =16x/8 =2x 2006-10-28 18:19:51 補充： NO.1Ax=(7x-3Bx)/8=[7x-3*(-3)x]/8=[7x-(-9)x]/8=(7x+9x)/8=16x/8=2xAx=2xA=2 2006-10-28 18:20:34 補充： NO.22(x^2-1)+Ax=(x+B)(Cx-1)L.H.S.=2(x^2-1)+Ax =2x^2-2+AxR.H.S.=(x+B)(Cx-1) =(Cx-1)x+(Cx-1)B =Cx^2-x+CBx-Bso, 2x^2-2+Ax=Cx^2-x+CBx-BBy comparing like terms,C=2B=-2Ax=CBx-x =2*(-2)*x-x =-4x-x =-5xAx=-5xA=-5|||||(8A+3B)x +2B≡7x-6 L.H.S. = (8A+3B)x +2B R.H.S. = 7x-6 ∴(8A+3B)x +2B≡7x-6 By the comparing of the like terms, we have, 2B=-6 B=-3 (8A+3B)=7 8A+3(-3)=7 8A-9=7 8A=16 A=16/8 A=2