Bai 1:
a, cho x+y=7 . Tinh M= (x+y)3+2x2+4xy+2y2
b, cho x-y=7 . Tinh A = x.(x+2)+y.(y-2)-2xy+37
GIUP MINH NHA, THANK YOU!^^
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
4 tháng 7 2017
\(A=x\left(x+2\right)+y\left(y-2\right)-2xy+37\)
\(=x^2+2x+y^2-2y-2xy+37\)
\(=\left(x^2-2xy+y^2\right)+2\left(x-y\right)+37\)
\(=\left(x-y\right)^2+2\left(x-y\right)+37\)
Thay x - y = 7
\(\Rightarrow A=49+14+37=100\)
Vậy A = 100 khi x - y = 7
8 tháng 7 2017
a, Ta có
A= x(x+2)+y(y-2)-2xy +37
=x2+2x+y2-2y-2xy+37
=x2-2xy+y2+2(x-y)+37
=(x-y)2+2(x-y)+37
Vì x-y=7
=>(x-y)2+2(x-y)+37=72+14+37=100
KL
b, Ta có B=x2+4y2-2x+10+4xy-4y
=x2+4xy+4y2-2x-4y+10
=(x+2y)2-2(x+2y)+10
Vì x+2y=5
=>(x+2y)2-2(x+2y)+10=52-10+10=25
KL
DT
0
12 tháng 8 2018
a) \(A=x\left(x+2\right)+y\left(y-2\right)-2xy+37\)
\(A=x^2+2x+y^2-2y-2xy+37\)
\(A=\left(x^2-2xy+y^2\right)+\left(2x-2y\right)+37\)
\(A=\left(x-y\right)^2+2\left(x-y\right)+37\)
Mà \(x-y=7\)
\(\Rightarrow A=7^2+2.7+37\)
\(A=100\)
b) \(B=x^2+4y^2-2x+10+4xy-4y\)
\(B=\left(x^2+4xy+4y^2\right)-\left(2x+4y\right)+10\)
\(B=\left(x+2y\right)^2-2\left(x+2y\right)+10\)
Mà \(x+2y=5\)
\(\Rightarrow B=5^2-2.5+10\)
\(B=25\)
22 tháng 5 2022
b: \(x^2+y^2=\left(x+y\right)^2-2xy=25-12=13\)
c: \(\left(x-y\right)^2=\left(x+y\right)^2-4xy=5^2-4\cdot6=1\)
=>x-y=1 hoặc x-y=-1
25 tháng 5 2022
Câu 2:
\(B=x^2+2x+y^2-2x-2xy+37\)
\(=\left(x^2-2xy+y^2\right)+2\left(x-y\right)+37\)
\(=\left(x-y\right)^2+2\left(x-y\right)+37\)
\(=7^2+2\cdot7+37=49+37+14=100\)
Câu 3:
\(C=\left(x^2+4xy+4y^2\right)-2\left(x+2y\right)+10\)
\(=\left(x+2y\right)^2-2\left(x+2y\right)+10\)
\(=5^2-2\cdot5+10=25\)
3 tháng 10 2017
Bài 1 câu g bạn kia làm sai mình sửa lại nhá
\(3a^2-6ab+3b^2-12c^2\)
\(=3\left(a^2-2ab+b^2\right)-12c^2\)
\(=3\left(a-b\right)^2-12c^2\)
\(=3\left[\left(a-b\right)^2-4c^2\right]\)
\(=3\left(a-b-2c\right)\left(a-b+2c\right)\)
3 tháng 10 2017
Để mình làm tiếp cho :))
Bài 2 :
Câu a : \(37,5.8,5-7,5.3,4-6,6.7,5+1,5.37,5\)
\(=\left(37,5.8,5+1,5.37,5\right)-\left(7,5.3,4+6,6.7,5\right)\)
\(=37,5\left(8,5+1,5\right)-7,5\left(3,4+6,6\right)\)
\(=37,5.10-7,5.10\)
\(=10.30=300\)
Câu b : \(35^2+40^2-25^2+80.35\)
\(=\left(35^2+80.35+40^2\right)-25^2\)
\(=\left(30+45\right)^2-25^2\)
\(=75^2-25^2\)
\(=\left(75+25\right)\left(75-25\right)\)
\(=100.50=5000\)
Bài 3 :
Câu a : \(x^3-\dfrac{1}{9}x=0\)
\(\Leftrightarrow x\left(x^2-\dfrac{1}{9}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x^2-\dfrac{1}{9}=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=\pm\dfrac{1}{3}\end{matrix}\right.\)
Câu b : \(2x-2y-x^2+2xy-y^2=0\)
\(\Leftrightarrow2\left(x-y\right)-\left(x-y\right)^2=0\)
\(\Leftrightarrow\left(x-y\right)\left(2-x+y\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-y=0\\2-x+y=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=y\\x+y=2\Rightarrow x=2-y\end{matrix}\right.\)
Câu c :
\(x\left(x-3\right)+x-3=0\)
\(\Leftrightarrow\left(x-3\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3\\x=-1\end{matrix}\right.\)
\(x^2\left(x-3\right)+27-9x=0\)
\(\Leftrightarrow x^2\left(x-3\right)-9\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x^2-9\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x^2-9=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3\\x=\pm3\end{matrix}\right.\)
Bài 4 :
Câu a :
\(x^2-4x+3\)
\(=x^2-x-3x+3\)
\(=\left(x^2-x\right)-\left(3x-3\right)\)
\(=x\left(x-1\right)-3\left(x-1\right)\)
\(=\left(x-1\right)\left(x-3\right)\)
Câu b :
\(x^2+x-6\)
\(=x^2-2x+3x-6\)
\(=x\left(x-2\right)+3\left(x-2\right)\)
\(=\left(x-2\right)\left(x+3\right)\)
Câu c :
\(x^2-5x+6\)
\(=x^2-2x-3x+6\)
\(=\left(x^2-2x\right)-\left(3x-6\right)\)
\(=x\left(x-2\right)-3\left(x-2\right)\)
\(=\left(x-2\right)\left(x-3\right)\)
Câu d :
\(x^4+4\)
\(=x^4+4x^2+4-4x^2\)
\(=\left(x^2+2\right)^2-\left(2x\right)^2\)
\(=\left(x^2+2-2x\right)\left(x^2+2+2x\right)\)
QT
1
13 tháng 7 2019
a) Ta có: A = (x + y)3 + 2x2 + 4xy + 2y2
A = 73 + 2(x2 + 2xy + y2)
A = 343 + 2(x + y)2
A = 343 + 2. 72
A = 343 + 98 = 441
b) B = (x - y)3 - x2 + 2xy - y2
=> B = (-5)3 - (x2 - 2xy + y2)
=> B = -125 - (x - y)2
=> B = -125 - (-5)2
=> B = -125 - 25 = -150
a: \(M=\left(x+y\right)^3+2\left(x^2+2xy+y^2\right)\)
\(=\left(x+y\right)^3+2\left(x+y\right)^2\)
\(=7^3+2\cdot49=441\)
b: \(A=x^2+2x+y^2-2y-2xy+37\)
\(=\left(x-y\right)^2+2\left(x-y\right)+37\)
\(=7^2+2\cdot7+37\)
\(=49+14+37=100\)