若x²+4y²+2x-4y+2=0,求根号下5x²+16y²的值
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若x²+4y²+2x-4y+2=0,求根号下5x²+16y²的值
若x²+4y²+2x-4y+2=0,求根号下5x²+16y²的值
若x²+4y²+2x-4y+2=0,求根号下5x²+16y²的值
x²+4y²+2x-4y+2=0
(x+1)²+(2y-1)²=0
x+1=0
2y-1=0
x=-1
y=1/2
根号下5x²+16y²
=根号下5*1+16*1/4
=根号下5+4
=根号9
=3
x=-1,y=1/2
原式=根号5+4=93
x²+4y²+2x-4y+2=0配方得(x+1)²+(2y-1)²=0
由平方和为0性质得:x+1=0且2y-1=0
所以x=-1且y=1/2
所以有:根号下5x²+16y²
=根号下5*1+16*1/4
=根号下5+4
=根号9
=3