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(1)计算:(-)×; (2)解方程:+3=.
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解方程4x-3=2x-1
解方程x+1²=2x-3²
解方程3x﹣7x﹣1=3﹣2x+3
解方程12﹣22x+1=31+x
解方程3x﹣1+1=5x+2.
解方程22x-2+1=2x-x-3
解方程3x-7x-1=3-2x+3
解方程x2+1=3x.
解方程3x-2=1-2x+1
解方程x2+1=3x
解方程5-23y-1=1
阅读下面的解题过程解方程|x+3|=2.解当x+3≥0时原方程可化成为x+3=2解得x=-1经检验x
我们规定若关于x的一元一次方程ax=b的解为b﹣a则称该方程为差解方程例如2x=4的解为2且2=4﹣
解方程3y+12=25
解方程x-1=22x+3
下列解方程的过程中正确的是
x
2
=-2,解方程,得x=±
(x-2)
2
=4,解方程,得x-2=2,x=4
4(x-1)
2
=9,解方程,得4(x-1)=±3,x
1
=
,x
2
=
(2x+3)
2
=25,解方程,得2x+3=±5,x
1
=1,x
2
=-4
理解同解方程的定义再解题1同解方程的定义为如果两个方程的解相同那么这两个方程叫同解方程反之如果两个方
解方程3xx-1=2x-2.
解方程x2+3x+1=0.
解方程x+1-2x-1=1-3x
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实验室用溶质质量分数为6%的氯化钠溶液配制50g溶质质量分数为3%的氯化钠溶液.下列说法正确的是
图中所示的图象中能正确反映对应变化关系的是
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如图所示的四个图象不能正确反映对应变化关系的是
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最近科学家用钙原子轰击铕原子合成117号元素部分信息如图所示.下列说法错误的是
下列对如图所示实验的分析不正确的是
Umbrellasprotectpeoplefromtherainbutthecurrentdesignisfarfromperfect.Theyfolddownintosoakeddroppingmesses.Theycrumple起皱whenhitbypowerfulblastsofwind. Ahandfulofdesignershaveputforththeirbestideasforrevisingsomeofthesedrawbacks.There'stheRainShieldwhichfeaturesanenlargedcoverthatextends.It'ssortoflikeatailonatuxedo燕尾服downoneside.Thisextracoverageguardsagainstincomingsplash.Italsopreventsforcefulwindsfromcatchingtheinsideoftheumbrella. TheSenzumbrellaisanotheroddly﹣shapedreboot.Itcomesintheshapeofastealth隐形fighter.Itisformulatedtochannelwindflowacrossthesurfaceinawaythatwon'tcauseittoturnover.ThecompanyclaimstheSenzcanwithstandwindsofupto70mph. Noneoftheseimprovementshoweverhasthemakingsofatrueevolutionaryleapfortheoldschoolraincover﹣atleastnotyet.Eachconceptwhilelesseningonedrawbackcreatesothers.ForexampletheRainShield'sunusualshaperequiresthattheuserskillfullytwistsitdowntosize. Therewardsforwhoeverimprovestheumbrellaaresubstantial可观的writesSusanOrleanintheNewYorker.TheannualretailmarketintheUnitedStatesaloneisnow$348million﹣about33millionumbrellas.Therestoftheworldincludingmanycultureswhereumbrellasareusedbothasrainprotectionandassunshadeconsumesmanyminionsmore. Butperhapswhenitcomesdowntoitpeoplehavegrowntoousedtotheumbrella.Ithasthenotablelookofaperfectlycircularhatonastickthatsimplyopensandfoldswhenweneedit.It'shardtoimproveontheumbrellawritesdesignerCharlesLimatCrookedPixels.Abetterumbrellawouldhavetobeeasiertorecycleorrepair.Oritwouldbeconstructedfromcarbonfibertomakeitbothdurableandlight.Butwhyevenbother?Umbrellasareperfectbecauseoftheirpriceandsize.It'sasatisfiedanddrymarket. 1WhatdoweknowabouttheRainShield? A.Itcanblackpeople'sviews. B.Itiseasytofolddownintomesses. C.Itcanchangethewindflowchannel. D.Itsenlargedcoverguardsagainstrainandwind. 2WhatdoesSusanOrleanthinkoftheimprovementofumbrellas? A.It'sworthwhile. B.It'gawasteoflabor. C.It'sfarfromperfect. D.Itmakesnodifference. 3AccordingtoCharlesLim. A.theumbrellawillnotsellwell B.presentumbrellasareeasytorecycle C.acompletelyperfectumbrellaishardtodesign D.idealumbrellaswouldbemadefromplastics 4Whatdoesthetextmainlyfocuson? A.Thefunctionsofumbrellas B.Inventingtheperfectumbrella C.Thedesignersofumbrellas D.Exploringthehistoryofumbrellas
下列实验操作中正确的是
某化学小组的同学将一枚洁净的铁钉放入食盐水中如图装置气密性良好一段时间后观察到装置中右侧导管的液面升高铁钉生锈试管底部有黑色固体物质请你分析并回答 1液面上升的原因是 2黑色固体一定含有碳该结论也得到了小组同学的认可理由是 3相信你一定在家中做过铁钉分别在水以及食盐水中生锈的实验你的结论之一是铁钉在填“水”或“食盐水”中生锈快.
下列对分子的认识说法不正确的是
下列说法正确的是
下列变化属于物理变化的是
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