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\(=\frac{41^2-39}{41^2+39^2+2.41.39}\)
\(=\frac{41^2-39}{41^2+2.41.39+39^2}\)
\(=\frac{41^2-39}{\left(41+39\right)^2}\)
\(\)
a,\(=\left(\frac{3}{5}x+\frac{2}{7}y\right)^2=\left(\frac{3}{5}.5+\frac{2}{7}.\left(-7\right)\right)^2=0\)
\(b,=\left(\frac{5}{4}u^2v+\frac{2}{25}v^2\right)^2=\left(\frac{5}{4}.\left(\frac{2}{5}\right)^2.5+\frac{2}{25}.5^2\right)^2=3^2=9\)
b: \(B=4^{30}+5^{30}=\left(4^2+5^2\right)\cdot A=41\cdot A⋮41\)
c: \(C=39^{13}+39^{20}=39^{13}\left(1+39^7\right)=39^{13}\left(39+1\right)\cdot G=39^{13}\cdot40\cdot G⋮40\)
f: \(=8\left(16^n-1\right)=8\left(16-1\right)\cdot H=120\cdot H⋮120\)
Bài 1:
\(a,413\left(413-26\right)+169\)
\(=413^2-26.413+13^2\)
\(=413^2-2.413.13+13^2\)
\(=\left(413-13\right)^2\)
\(=400^2\)
\(=160000\)
\(b,x^2+2x+1\)
\(=x^2+2.x.1+1^2\)
\(=\left(x+1\right)^2\)
\(=\left(99+1\right)^2\)
\(=100^2=10000\)
a) 9x2 - 36
= ( 3x)2 - 62
= ( 3x - 6)( 3x + 6)
b) ax - ay - bx + by
= a( x - y) - b( x - y)
= ( x - y)( a - b)
c) y3 - 4y2 + 3y
= y3 - y2 - 3y2 + 3y
= y2( y - 1) - 3y( y - 1)
= ( y - 1)( y2 - 3y)
= y( y - 3)( y - 1)
Pythagorean theorem: \(AD=\sqrt{BD^2-AB^2}=4\) (cm)
\(\Rightarrow BC=AD=4\left(cm\right)\)
\(CC'=\sqrt{BC'^2-BC^2}=4\sqrt{2}\)
The lateral surface area: \(2CC'.\left(BC+AB\right)=56\sqrt{2}\left(cm^2\right)\)
\(\frac{\left(2n+1\right)^3+n^3}{\left(n+1\right)^3-n^3}=\frac{\left(3n+1\right)\left(3n^2+3n+1\right)}{3n^2+3n+1}=3n+1\)
\(\Rightarrow A=\left(3.1+1\right)+\left(3.2+1\right)+...+\left(3.20+1\right)\)
\(=3\left(1+2+...+20\right)+20\)
\(=\frac{3.20.21}{2}+20=...\)
a) Ta có: \(413^2+213^2-326\cdot213\)
\(=413^2-2\cdot413\cdot213+213^2+106500\)
\(=200^2+106500\)
\(=40000+106500\)
\(=146500\)
1/\(\frac{84^2-16^2}{37^2-63^2}=\frac{\left(84-16\right)\left(84+16\right)}{\left(37-63\right)\left(37+63\right)}=\frac{68.100}{-26.100}=\frac{-68}{26}=\frac{-34}{13}\)
2/ \(199^2=\left(200-1\right)^2=40000-400+1=39601\)
3/ \(31^2=\left(30+1\right)^2=900+60+1=961\)
4/ \(45.55=\left(50-5\right)\left(50+5\right)=50^2-25=2500-25=2475\)
5/ \(78.82=\left(80-2\right)\left(80+2\right)=80^2-4=6400-4=6396\)
a) \(413.\left(413-26\right)+169=413^2-2.13.413+13^2=\left(413-13\right)^2=160000\)
b) \(\left(625^2+3\right).\left(25^4-3\right)-5^{16}+10\)
\(=\left(5^8+3\right)\left(5^8-3\right)-5^{16}+10\)
\(=5^{16}-9-5^{16}+10=1\)
c) \(\frac{41^2+39^2+8^2.39}{41^2-39^2}=\frac{\left(41+39\right)^2}{\left(41-39\right)\left(41+39\right)}=\frac{41+39}{41-39}=\frac{80}{2}=40\)