1. cho x-y=7 Tính:
a) A=x(x+2)+y(x-2)-2xy+37
b) B=x^3(x+1)-y^2(y-1)+xy-3xy(x-y+1)+100
Cho x-y=7.Tính:
a)x(x+2)+y(y-2)-2xy+37
b)\(x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)
Cho x-y=7. Tính :
a) P=x(x+2)+y(y-2)-2xy+37
b) Q=x2(x+1)-y2(y-1)+xy-3xy(x-y+1)-95
a) P = x(x + 2) + y(y - 2) - 2xy + 37
⇒ P = x2 + 2x + y2 - 2y - 2xy + 37
⇒ P = (x2 - 2xy + y2) + 2(x - y) + 37
⇒ P = (x - y)2 + 2.7 + 37
⇒ P = 72 +14 + 37
⇒ P = 49 + 51
⇒ P = 100
b) Q = x2(x + 1) - y2(y - 1) + xy - 3xy(x - y + 1) - 95
⇒ Q = x3 + x2 - y3 + y2 + xy - 3x2y + 3xy2 - 3xy - 95
⇒ Q = (x3 - 3x2y + 3xy2 - y3) + (x2 + xy - 3xy + y2) - 95
⇒ Q = (x - y)3 + (x - y)2 - 95
⇒ Q = 73 + 72 - 95
⇒ Q = 343 + 49 - 95
⇒ Q = 297
Cho x- y = 7 Tính GTBT
A=x(x+2)+y(y-2)-2xy+37
B=x3+x2-y3+y2+xy-3x2y+3xy2-3xy-9
C=x3-x2-y3-y2-3xy(x-y)+2xy
D=x2(x+1)-y2(y-1)+xy-3xy(x-y+1)-95
Giúp mình vs !!!!!
a) \(A=x\left(x+2\right)+y\left(y-2\right)-2xy+37\)
\(A=x^2+2x+y^2-2y-2xy+37\)
\(A=\left(x^2-2xy+y^2\right)+\left(2x-2y\right)+37\)
\(A=\left(x-y\right)^2+2\left(x-y\right)+37\)
\(A=\left(x-y\right)^2+2\left(x-y\right)+1+36\)
\(A=\left(x-y+1\right)^2+36\)
Thay x - y = 7 vào A
\(A=\left(7+1\right)^2+36\)
\(A=8^2+36\)
\(A=64+36\)
\(A=100\)
b) \(B=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-9\)
\(B=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+xy-3xy+y^2\right)-9\)
\(B=\left(x-y\right)^3+\left(x^2-2xy+y^2\right)-9\)
\(B=\left(x-y\right)^3+\left(x-y\right)^2-9\)
Thay x - y = 7 vào B
\(B=7^3+7^2-9\)
\(B=343+49-9\)
\(B=383\)
c) \(C=x^3-x^2-y^3-y^2-3xy\left(x-y\right)+2xy\)
\(C=\left[x^3-y^3-3xy\left(x-y\right)\right]-\left(x^2-2xy+y^2\right)\)
\(C=\left(x-y\right)^3-\left(x-y\right)^2\)
Thay x - y = 7 vào C
\(C=7^3-7^2\)
\(C=343-49\)
\(C=294\)
d) \(D=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)
\(D=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95\)
\(D=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2-2xy+y^2\right)-95\)
\(D=\left(x-y\right)^3+\left(x-y\right)^2-95\)
Thay x - y = 7 vào D
\(D=7^3+7^2-95\)
\(D=343+49-95\)
\(D=297\)
cho x-y=7 tính giá trị của các bt sau
a) A= x2+y2+4x-2xy+4y+2019
b) B=x3-3xy(x-y)-y3-x2+2xy-y2
c) C=x2(x+1)-y2(y-1)+xy-3xy(x-y+1)
Cho x-y=7.Tính:
1)A=x(x+2)+y(y-2)-2xy+37
2)\(B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-9^5\)
\(A=x\left(x+2\right)+y\left(y-2\right)-2xy+37\)
\(A=x^2+2x+y^2-2y-2xy+37\)
\(A=\left(x^2+y^2-2xy+1+2x-2y\right)+36\)
\(A=\left(x-y+1\right)^2+36\)
\(A=\left(7+1\right)^2+36\)
\(A=8^2+36\)
\(A=100\)
\(B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\) \((9^5\) \(sai\)\()\)
\(B=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95\)
\(B=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+xy-3xy+y^2\right)-95\)
\(B=\left(x-y\right)^3+\left(x^2-2xy+y^2\right)-95\)
\(B=\left(x-y\right)^3+\left(x-y\right)^2-95\)
\(B=7^3+7^2-95\)
\(B=297\)
Cho x-y=7
Tính:
a/ \(A=x^3-3xy\left(x-y\right)-y^3-x^2-2xy-y^2\)
b/ \(B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)
Ai muốn tích điểm thì làm giùm mk bài tập vs:
Bài 1: Cho x+y=5; xy=2. Tính (x-y)2
Bài 2: Cho x-y=6; xy=2. tính x+y
Bài 3: x-y=7. Tính A= x(x+2)+y(y-2)-2xy+37
Bài 4: x-y=5; x2+y2=15, Tính x3 - y3
Bài 5: x+y=3; x2 +y2 =5. Tính x3 +y3
Bài 6: Cho x-y=7. Tính M= x2(x+1)-y2(y-1)+xy-3xy(x-y+1)-95
Bài 7: Cho x-y=7. Tính M= x3-3xy(x-y)-y3-x2+2xy-y2
Bài 8: Tính M= a3 +b3 +3ab(a2+b2)+6a2b2(a+b)
Giúp mk vs. giúp đc bài nào thì giúp nha! Help!
Bài 8: Cho a+b= 1 nha ( mk thiếu đề)
Bài 1:
Theo bài ra ta có:
\(\left(x-y\right)^2=x^2-2xy+y^2\)
\(=\left(5-y\right)^2-2\times2+\left(5-x\right)^2\)
\(=5^2-2\times5y+y^2-4+5^2-2\times5x+x^2\)
\(=25-10y+y^2+25-10x+x^2-4\)
\(=\left(25+25\right)-\left(10x+10y\right)+x^2+y^2-4\)
\(=50-10\left(x+y\right)+x^2+2xy+y^2-2xy-4\)
\(=50-10\times5+\left(x+y\right)^2-2\times2-4\)
\(=50-50+5^2-4-4\)
\(=25-8=17\)
Vậy giá trị của \(\left(x-y\right)^2\)là 17
ta có : M=2.(a^3 +b^3) -3.(a^2 + b^2)
<=>M=2.(a+b)(a^2 -ab +b^2) - 3(a^2 +3b^2)
<=>M=2(a^2 -ab +b^2) -3(a^2 +b^2) vì a+b=1(gt)
<=>M=-(a^2 +b^2 +2ab)
<=>M=-(a+b)^2
<=>M=-1 (vì a+b=1)
Cho x-y=7.Tính:
a)x(x+2)+y(y-2)-2xy+37
b)\(x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)
a: \(=x^2+2x+y^2-2y-2xy+37\)
\(=\left(x-y\right)^2+2\left(x-y\right)+37\)
\(=7^2+2\cdot7+37=49+14+37=100\)
b: \(=x^3+x^2-y^3+y^2+xy-3xy\cdot\left(7+1\right)-95\)
\(=\left(x^3-y^3\right)+\left(x^2+y^2\right)+xy-24xy-95\)
\(=\left(x-y\right)^3+3xy\left(x-y\right)+\left(x-y\right)^2+2xy-23xy-95\)
\(=7^3+3xy\cdot7+49-21xy-95\)
\(=343+49-95=297\)
Cho x-y=7
Tính
a/ \(A=x^3-3xy\left(x-y\right)-y^3-x^2-2xy-y^2\)
b/ \(B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)