x^2-y^2-2xy-1 tại x=93;y=6
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a. 4 . 102 - 52 + 4 . 10 + 1
= 4 . 100 - 25 + 4 . 10 + 1
= 400 - 25 + 40 + 1
= 416
b. 932 - 62 - 2 . 6 - 2
= 8649 - 36 - 12 - 2
= 8599
a: Ta có: \(4x^2-y^2+4x+1\)
\(=\left(2x+1\right)^2-y^2\)
\(=\left(2x+y-1\right)\left(2x-y-1\right)\)
\(=\left(20+5-1\right)\left(20-5-1\right)\)
\(=24\cdot14=336\)
\(=4x^2y^2+2xy-6-4x^2y^2+4xy-1=6xy-7=6\cdot\dfrac{1}{3}\cdot3-7=6-7=-1\)
\(x^2-y^2-2y-1\)
\(=x^2-\left(y+1\right)^2\)
\(=\left(x-y-1\right)\left(x+y+1\right)\)
\(=100\cdot\left(93-6-1\right)\)
=8600
\(A=\left(x-y\right)^3=\left(\dfrac{1}{5}-\dfrac{1}{3}\right)^3=\left(-\dfrac{2}{15}\right)^3=-\dfrac{8}{1375}\)
1, \(x^2+2xy+y^2=\left(x+y\right)^2\)
2, \(4x^2+12x+9=\left(2x\right)^2+2\cdot3\cdot2x+3^2=\left(2x+3\right)^2\)
3, \(x^2+5x+\dfrac{25}{4}=x^2+2\cdot\dfrac{5}{2}\cdot x+\left(\dfrac{5}{2}\right)^2=\left(x+\dfrac{5}{2}\right)^2\)
4, \(16x^2-8x+1=\left(4x\right)^2-2\cdot4x\cdot1+1^2=\left(4x-1\right)^2\)
5, \(x^2+x+\dfrac{1}{4}=x^2+2\cdot\dfrac{1}{2}\cdot x+\left(\dfrac{1}{2}\right)^2=\left(x+\dfrac{1}{2}\right)^2\)
1: =(x+y)^2
2: =(2x+3)^2
3: =(x+5/2)^2
4: =(4x-1)^2
5: =(x+1/2)^2
6: =(x-3/2)^2
7: =(x+1)^3
8: =(1/2x+1)^2
9: =(3y-1/3)^3
10: =(2x+y)^3
a: \(x^2+x-2x-2\)
\(=x\left(x+1\right)-2\left(x+1\right)\)
\(=\left(x+1\right)\left(x-2\right)=\left(-1+1\right)\left(-1-2\right)=0\)
b: \(3x^2-2x+9x-6\)
\(=x\left(3x-2\right)+3\left(3x-2\right)\)
\(=\left(3x-2\right)\left(x+3\right)=\left(3\cdot7-2\right)\left(7+3\right)\)
\(=19\cdot10=190\)
c: \(2x^2-3xy-xy^2\)
\(=x\left(2x-3y-y^2\right)\)
\(=2\left(2\cdot2-3\cdot3-9\right)\)
\(=2\cdot\left(4-18\right)=-28\)
Đề là gì thế bạn ?
\(x^2-y^2+2xy-1\)
\(=\left(x-y\right)^2-1\)
\(=\left(x-y-1\right)\left(x-y+1\right)\)
\(=\left(93-6-1\right)\left(93-6+1\right)\)
\(=86\cdot88=7568\)