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一、填空题(本大题共10小题,每小题3分,共30分)1·计算:(-2)×(-3)=·2·化简:-a2+2a2=·3·方程x2-2x=0的解是·4·如图,在△ABC中,∠ACB=90°,∠ABC=25°,CD⊥AB于D,则∠ACD=度·5·收音机刻度盘的波长l和频率f分别是用米(m)和千赫兹(kHz)为单位标刻的·波长l和频率f满足关系
First, fill in the blank title (this big question a total of 10 small questions, each small question 3 points, a total of 30 points) 1 calculation: (-2) × (-3) = · 2 · Simplification: -a2+2a2 = · 3 The solution of the equation x2-2x=0 is ··················································································收音机· The wavelength l and the frequency f are respectively marked in meters (m) and kilohertz (kHz). The wavelength l and the frequency f satisfy the relationship