標題:
e幾條數5識做?幫下我?
發問:
1 (x+1)(x-1)+(x2次方+1) 2 (x+3)(x-3)+(x2次方+9) 3 (x+2)2次方-(x-2)2次方 4 (x+y+z)(x-y-z) 5 (2a+b+1)(2a+b-1)
最佳解答:
1 (x+1)(x-1)+(x2次方+1) = (x+1)(x-1)+(x^2 +1) = x^2 -1 + x^2+1 = 2x^2 2 (x+3)(x-3)+(x2次方+9) = (x+3)(x-3)+(x^2 +9) = x^2 - 9 + x^2 + 9 = 2x^2 3 (x+2)2次方-(x-2)2次方 = (x+2)^2 - (x-2)^2 = x^2 + 4x + 4 - (x^2 - 4x + 4) = x^2 + 4x + 4 - x^2 + 4x -4 = 8x 4 (x+y+z)(x-y-z) = x^2 - xy - xz + xy -y^2 - yz + xz - yz -z^2 = x^2 - y^2 - z^2 - 2yz 5 (2a+b+1)(2a+b-1) = 4a^2 + 2ab -2a + 2ab + b^2 -b +2a +b -1 = 4a^2 + b^2 +4ab -1 2008-05-14 09:56:01 補充： 4 (x+y+z)(x-y-z) 也可用以下: = (x + (y+z))(x - (y+z)) = x^2 - (y+z)^2 = x^2 - (y^2 + 2yz + z^2) = x^2 - y^2 - z^2 - 2yz 5 (2a+b+1)(2a+b-1) 也可這樣: = ((2a+b) + 1)((2a+b) -1) = (2a+b)^2 -1 = 4a^2 + 4ab + b^2 -1
其他解答:
e幾條數5識做?幫下我?
發問:
1 (x+1)(x-1)+(x2次方+1) 2 (x+3)(x-3)+(x2次方+9) 3 (x+2)2次方-(x-2)2次方 4 (x+y+z)(x-y-z) 5 (2a+b+1)(2a+b-1)
最佳解答:
1 (x+1)(x-1)+(x2次方+1) = (x+1)(x-1)+(x^2 +1) = x^2 -1 + x^2+1 = 2x^2 2 (x+3)(x-3)+(x2次方+9) = (x+3)(x-3)+(x^2 +9) = x^2 - 9 + x^2 + 9 = 2x^2 3 (x+2)2次方-(x-2)2次方 = (x+2)^2 - (x-2)^2 = x^2 + 4x + 4 - (x^2 - 4x + 4) = x^2 + 4x + 4 - x^2 + 4x -4 = 8x 4 (x+y+z)(x-y-z) = x^2 - xy - xz + xy -y^2 - yz + xz - yz -z^2 = x^2 - y^2 - z^2 - 2yz 5 (2a+b+1)(2a+b-1) = 4a^2 + 2ab -2a + 2ab + b^2 -b +2a +b -1 = 4a^2 + b^2 +4ab -1 2008-05-14 09:56:01 補充： 4 (x+y+z)(x-y-z) 也可用以下: = (x + (y+z))(x - (y+z)) = x^2 - (y+z)^2 = x^2 - (y^2 + 2yz + z^2) = x^2 - y^2 - z^2 - 2yz 5 (2a+b+1)(2a+b-1) 也可這樣: = ((2a+b) + 1)((2a+b) -1) = (2a+b)^2 -1 = 4a^2 + 4ab + b^2 -1
其他解答:
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