已知:y1=5x²+7x+1,y2=x²-9x-15 则当x=?y1=y2

已知:y1=5x²+7x+1,y2=x²-9x-15 则当x=?y1=y2

y1=y2
5x^2+7x+1=x^2-9x-15
4x^2+16x+16=0
x^2+4x+4=0
(x+2)^2=0
x=-2
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