Which planet is the closest planet to the sun, Mercury, Mars

Which planet is the closest planet to the sun, Mercury, Mars, Venus or Jupiter?

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What kind of new technology helped us a lot to study the pla

What kind of new technology helped us a lot to study the planets?

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(本小题满分13分) 抛物线的顶点在原点,焦点为椭圆X2+5y2=5的左焦点,过点M(-1,-1)引抛物线的弦,使M为弦

(本小题满分13分) 抛物线的顶点在原点,焦点为椭圆X2+5y2=5的左焦点,过点M(-1,-1)引抛物线的弦,使M为弦的中点,求弦所在直线的方程,并求出弦长

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f[f(x)]=x4-6x2+6,则f(x)为 ( )

f[f(x)]=x4-6x2+6,则f(x)为 ( ) A.f(x)=x2-3 B.f(x)=x2-12 C.f(x)=x2+6 D.f(x)=x2-6

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