Tính:
100x2=(x2+25)2
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a) \(100x^2-\left(x^2+25\right)^2\)
\(=\left(10x\right)^2-\left(x^2+25\right)^2\)
\(=\left(10x+x^2+25\right)\left(10x-x^2-25\right)\)
\(=\left(x+5\right)^2\left(10x-x^2-25\right)\)
b) \(1+\left(x-y+5\right)^2-2\left(x-y+5\right)\)
\(=\left[\left(x-y+5\right)-1\right]^2\)
\(=\left(x-y+4\right)^2\)
c) \(\left(x^2+4y^2-5\right)^2-16\left(x^2y^2+2xy+1\right)\)
\(=\left(x^2+4y^2-5\right)^2-4^2\left(xy+1\right)^2\)
\(=\left[\left(x^2+4y^2-5\right)-4\left(xy+1\right)\right]\left[\left(x^2+4y^2-5\right)+4\left(xy+1\right)\right]\)
\(=\left(x^2+4y^2-5-4xy-4\right)\left(x^2+4y^2-5+4xy+4\right)\)
\(=\left(x^2-4xy+4y^2-9\right)\left(x^2+4xy+4y^2-1\right)\)
\(=\left[\left(x-2y\right)^2-3^2\right]\left[\left(x+2y\right)^2-1^2\right]\)
\(=\left(x-2y-3\right)\left(x-2y+3\right)\left(x+2y-1\right)\left(x+2y+1\right)\)
d) \(\left(x^2+8x-34\right)^2-\left(3x^2-8x-2\right)^2\)
\(=\left[\left(x^2+8x-34\right)-\left(3x^2-8x-2\right)\right]\left[\left(x^2+8x-34\right)+\left(3x^2-8x-2\right)\right]\)
\(=\left(x^2+8x-34-3x^2+8x+2\right)\left(x^2+8x-34+3x^2-8x-2\right)\)
\(=\left(-2x^2+16x-32\right)\left(4x^2-36\right)\)
\(=-2\left(x^2-8x+16\right)\left[\left(2x\right)^2-6^2\right]\)
\(=-2\left(x-4\right)^2\left(2x-6\right)\left(2x+6\right)\)
\(=-2\left(x-4\right)^24\left(x-3\right)\left(x+3\right)\)
\(=8\left(x-4\right)^2\left(x-3\right)\left(x+3\right)\)
100+100x9+100x2-100
= 100*1+100x9+100x2-100*1
= 100 * (1+9+2-1)
= 100* 11
= 1100
900000000000 : 9 : 100 x 2 = 100000000000 : 100 x 2 = 1000000000 x 2 = 2000000000
x=99 nên x+1=100
A=x^5-x^4(x+1)+x^3(x+1)-x^2(x+1)+x(x+1)-9
=x^5-x^5-x^4+x^4+...+x^2+x-9
=x-9
=90
987+(100x2)+3):2=
987 + (200 + 3) : 2
987 + 203 : 2
= 987 + 101,5
= 1088,5
987+(100x2)+3):2=?
987+(200+3):2=?
987+203:2=?
987+101,5=?
1088,5=?
Vậy số cần tìm là 1088,5
Với x = 20040, ta có: A = 10/20040 = 1/2004.
Vậy A = 1/2004 khi x = 20040.
Ta có:P=x3+y3+2xy=(x+y)3−3xy(x+y)+2xy=2013−601xyP=x3+y3+2xy=(x+y)3−3xy(x+y)+2xy=2013−601xy
Đặt S=xy=x(201−x)S=xy=x(201−x)
Dễ có:1≤x≤2001≤x≤200
S=200−(x−1)(x−200)≥0⇒Smin=200S=200−(x−1)(x−200)≥0⇒Smin=200
Không mất tính TQ giả sử x≤y⇒x≤100x≤y⇒x≤100
S=100.101−(x−100)(x−101)≤100.101⇒Smax=100.101
Với x = 20040, ta có: A = 10/20040 = 1/2004.
Vậy A = 1/2004 khi x = 20040.
100x2 = (x2 + 25)2
<=> (10x)2 = (x2 + 25)2
<=> 10x = x2 + 25
<=> x2 - 10x + 52 = 0
<=> (x - 5)2 = 0
<=> x - 5 = 0
<=> x = 5
<=> 100x2 = (x2 + 25)2 = 100 . 25 = 2500
\(100x^2=\left(x^2+25\right)^2\)
\(\Leftrightarrow\left(x^2+25\right)^2=\left(\pm10x\right)^2\)
Mà \(x^2+25>0\)nên \(x^2+25=10x\)
\(\Leftrightarrow\left(x-5\right)^2=0\)
\(\Leftrightarrow x-5=0\Leftrightarrow x=5\)