急 下面下面1.计算①25a²-80a+64②14xy²-49x²y-y³③9-12(a-b)+4(a-b)²④2mx²-4mxy+2my²⑤x³-25x若a²+b²-4a-2b+5=0,求a和b的值上面 ² 是平方 ,&
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![急 下面下面1.计算①25a²-80a+64②14xy²-49x²y-y³③9-12(a-b)+4(a-b)²④2mx²-4mxy+2my²⑤x³-25x若a²+b²-4a-2b+5=0,求a和b的值上面 ² 是平方 ,&](/uploads/image/z/8978365-37-5.jpg?t=%E6%80%A5+%E4%B8%8B%E9%9D%A2%E4%B8%8B%E9%9D%A21.%E8%AE%A1%E7%AE%97%E2%91%A025a%26%23178%3B%EF%BC%8D80a%EF%BC%8B64%E2%91%A114xy%26%23178%3B%EF%BC%8D49x%26%23178%3By%EF%BC%8Dy%26%23179%3B%E2%91%A29%EF%BC%8D12%EF%BC%88a%EF%BC%8Db%EF%BC%89%EF%BC%8B4%EF%BC%88a%EF%BC%8Db%EF%BC%89%26%23178%3B%E2%91%A32mx%26%23178%3B%EF%BC%8D4mxy%EF%BC%8B2my%26%23178%3B%E2%91%A4x%26%23179%3B%EF%BC%8D25x%E8%8B%A5a%26%23178%3B%EF%BC%8Bb%26%23178%3B%EF%BC%8D4a%EF%BC%8D2b%EF%BC%8B5%EF%BC%9D0%2C%E6%B1%82a%E5%92%8Cb%E7%9A%84%E5%80%BC%E4%B8%8A%E9%9D%A2+%26%23178%3B+%E6%98%AF%E5%B9%B3%E6%96%B9+%2C%26)
急 下面下面1.计算①25a²-80a+64②14xy²-49x²y-y³③9-12(a-b)+4(a-b)²④2mx²-4mxy+2my²⑤x³-25x若a²+b²-4a-2b+5=0,求a和b的值上面 ² 是平方 ,&
急 下面下面
1.计算
①25a²-80a+64
②14xy²-49x²y-y³
③9-12(a-b)+4(a-b)²
④2mx²-4mxy+2my²
⑤x³-25x
若a²+b²-4a-2b+5=0,求a和b的值
上面 ² 是平方 ,³ 是立方
急 下面下面1.计算①25a²-80a+64②14xy²-49x²y-y³③9-12(a-b)+4(a-b)²④2mx²-4mxy+2my²⑤x³-25x若a²+b²-4a-2b+5=0,求a和b的值上面 ² 是平方 ,&
1.计算
①25a²-80a+64
= (5a-8)²
②14xy²-49x²y-y³
= y(14xy-49x²-y²)
= - y(7x+y)²
③9-12(a-b)+4(a-b)²
=(2a-2b-3)²
④2mx²-4mxy+2my²
= 2m(x²-2xy+y²)
=2m(x-y)²
⑤x³-25x
=x(x²-25)
=x(x+5)(x-5)
a²+b²-4a-2b+5=0
a²-4a+4+b²-2b+1=0
(a-2)²+(b-1)²=0
a-2=0
b-1=0
所以
a=2
b=1
第一题后面都是等于o吗??
1。计算
①25a²-80a+64
= (5a-8)²
②14xy²-49x²y-y³
= y(14xy-49x²-y²)
= - y(7x+y)²
③9-12(a-b)+4(a-b)²
=(2a-2b-3)²
④2mx²-...
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1。计算
①25a²-80a+64
= (5a-8)²
②14xy²-49x²y-y³
= y(14xy-49x²-y²)
= - y(7x+y)²
③9-12(a-b)+4(a-b)²
=(2a-2b-3)²
④2mx²-4mxy+2my²
= 2m(x²-2xy+y²)
=2m(x-y)²
⑤x³-25x
=x(x²-25)
=x(x+5)(x-5)
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①25a²-80a+64=(5a-8)^2;;;②14xy²-49x²y-y³= -y(y-7x)^2;;;;③9-12(a-b)+4(a-b)²=(2(a-b)-3)^2;;;④2mx²-4mxy+2my²=2m(y-x)^2;;;;⑤x³-25x=x(x-5)(x+5);;;;;;;;;a²+b²...
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①25a²-80a+64=(5a-8)^2;;;②14xy²-49x²y-y³= -y(y-7x)^2;;;;③9-12(a-b)+4(a-b)²=(2(a-b)-3)^2;;;④2mx²-4mxy+2my²=2m(y-x)^2;;;;⑤x³-25x=x(x-5)(x+5);;;;;;;;;a²+b²-4a-2b+5=0,,转化成,(a-2)^2+(b-1)^2=0,因为(a-2)^2>=0,(b-1)^2>=0,因此,a=2,b=1
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