x^2-(x-1)^2-[(x-1)^2-(x-2)^2]=2

问题描述:

x^2-(x-1)^2-[(x-1)^2-(x-2)^2]=2
^2表示平方

公式:a^2 - b^2 = (a + b) * (a - b)
所以:
x^2-(x-1)^2 = (x + x - 1) * (x - x + 1) = 2x - 1
(x-1)^2-(x-2)^2 = (x - 1 + x - 2) * (x - 1 - x + 2) = 2x - 3
因此:
x^2-(x-1)^2-[(x-1)^2-(x-2)^2] = (2x - 1) - (2x - 3) = 2
完毕