Question

因式分解法解一元二次方程题,顺便告诉一下秘诀

Answer 1

m^2-n^2 = (m+n)(m-n)

x^2+2mx+m^2-n^2=0

(x+m-n)(x+m+n) = 0

x1=n-m x2=-n-m

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(a^2/4)-b^2 = (a/2+b)(a/2-b)

x^2-ax+(a^2/4)-b^2=0

(x-a/2+b)(x-a/2-b)=0

x1=a/2+b x2=a/2-b

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x^2-bx-2b^2=0

(x - 2b)(x + b) = 0

x1 = 2b x2 = -b

秘诀就是靠RP...