数学题!!!急!!(因式分解)
利用分解因式计算(1)16.8*32分之7+7.6*16分之7=__________(2)1.22²*9-1.33²*4=___________(3)...
利用分解因式计算
(1)16.8*32分之7+7.6*16分之7=__________
(2)1.22²*9-1.33²*4=___________
(3)5*998+10=__________
(4)若X-Y=5,XY=6,则X²Y-XY²=______;2X²+2Y²=_______
(5)若X+Y+Z+2,X²-(Y-Z)²=8时X-Y-Z=_____ 展开
(1)16.8*32分之7+7.6*16分之7=__________
(2)1.22²*9-1.33²*4=___________
(3)5*998+10=__________
(4)若X-Y=5,XY=6,则X²Y-XY²=______;2X²+2Y²=_______
(5)若X+Y+Z+2,X²-(Y-Z)²=8时X-Y-Z=_____ 展开
3个回答
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(1)16.8*32分之7+7.6*16分之7=_____7_____
16.8*7/32+7.6*7/16
=8.4*7/16+7.6*7/16
=7/16*(8.4+7.6)
=7/16*16
=7
(2)1.22²*9-1.33²*4=___6.32________
1.22²*9-1.33²*4
=(1.22*3-1.33*2)(1.22*3+1.33*2)
=(3.66-2.66)(3.66+2.66)
=1*6.32
=6.32
(3)5*998+10=______5000____
5*998+10
=5*(1000-2)+10
=5*1000-5*2+10
=5000-10+10
=5000
(4)若X-Y=5,XY=6,则X²Y-XY²=___30___;2X²+2Y²=__74_____
X²Y-XY²
=xy(x-y)
=5*6
=30
2X²+2Y²
=2(x²+y²)
=2(x²-2xy+y²)+4xy
=2(x-y)²+4xy
=2*5^2+4*6
=50+24
=74
(5)若X+Y+Z+2,X²-(Y-Z)²=8时X-Y-Z=_____
???
16.8*7/32+7.6*7/16
=8.4*7/16+7.6*7/16
=7/16*(8.4+7.6)
=7/16*16
=7
(2)1.22²*9-1.33²*4=___6.32________
1.22²*9-1.33²*4
=(1.22*3-1.33*2)(1.22*3+1.33*2)
=(3.66-2.66)(3.66+2.66)
=1*6.32
=6.32
(3)5*998+10=______5000____
5*998+10
=5*(1000-2)+10
=5*1000-5*2+10
=5000-10+10
=5000
(4)若X-Y=5,XY=6,则X²Y-XY²=___30___;2X²+2Y²=__74_____
X²Y-XY²
=xy(x-y)
=5*6
=30
2X²+2Y²
=2(x²+y²)
=2(x²-2xy+y²)+4xy
=2(x-y)²+4xy
=2*5^2+4*6
=50+24
=74
(5)若X+Y+Z+2,X²-(Y-Z)²=8时X-Y-Z=_____
???
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第5问打错了吧,应该X+Y+Z=2
这样的话就有解了,这种程度的题要自己做啊,太简单了啊。有点自信,加油!
这样的话就有解了,这种程度的题要自己做啊,太简单了啊。有点自信,加油!
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(1)16.8*32分之7+7.6*16分之7=(16.8*7+7.6*2*7)/32=7*(16.8+15.2)/32=7
(2)1.22²*9-1.33²*4=(1.22*3)²-(1.33*2)²=(3.66+2.66)*(3.66-2.66)=6.32
(3)5*998+10=_5*1000-5*2+10=5000
(4)若X-Y=5,XY=6,则X²Y-XY²=__xy*(x-y)=30.;
因为(X-Y)²=5²
x²+y²-2xy=25;x²+y²-2*6=25
所以x²+y²=37
2X²+2Y²=74_
第五题可能你打错了已知条件
(5)若X+Y+Z=2,X²-(Y+Z)²=8时,就是X²-(Y+Z)²=(x-y-z)(x+y+z)=8
(x-y-z)×2=8
所以X-Y-Z=4
(2)1.22²*9-1.33²*4=(1.22*3)²-(1.33*2)²=(3.66+2.66)*(3.66-2.66)=6.32
(3)5*998+10=_5*1000-5*2+10=5000
(4)若X-Y=5,XY=6,则X²Y-XY²=__xy*(x-y)=30.;
因为(X-Y)²=5²
x²+y²-2xy=25;x²+y²-2*6=25
所以x²+y²=37
2X²+2Y²=74_
第五题可能你打错了已知条件
(5)若X+Y+Z=2,X²-(Y+Z)²=8时,就是X²-(Y+Z)²=(x-y-z)(x+y+z)=8
(x-y-z)×2=8
所以X-Y-Z=4
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