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a) \(105^3-15.105^2+75.105-125\)
\(=105^3-3.105^2.5+3.105.5^2-5^3\)
\(=\left(105-5\right)^3\)
\(=100^3=1000000\)
b) \(63^2-27^2+72^2-18^2\)
\(=\left(63-27\right)\left(63+27\right)+\left(72-18\right)\left(72+18\right)\)
\(=36.90+54.90\)
\(=90.90=8100\)
\(A=2004^2-16=\left(2004-4\right)\left(2004+4\right)=2000\cdot2008=4016000\)
\(B=892^2+892\cdot216+108^2=892^2+2\cdot892\cdot108+108^2=\left(892+108\right)^2=1000^2=1000000\)
\(C=10,2\cdot9,8-9,8\cdot0,2+10,2^2-10,2\cdot0,2\)
\(=9,8\left(10,2-0,2\right)+10,2\left(10,2-0,2\right)\)
\(=10\cdot\left(9,8+10,2\right)=10\cdot20=200\)
\(D=36^2+26^2-52\cdot36=\left(36-26\right)^2=10^2=100\)
\(E=105^2-25=\left(105-5\right)\left(105+5\right)=100\cdot110=11000\)
\(F=73^2-27^2=\left(73-27\right)\left(73+27\right)=46\cdot100=4600\)
A. 20042-16=20042-42=(2004-4)(2004+4)=2000.2008=2016000
B. 8922+892.216+1082= 8922+2.892.108+1082=(892+108)2=10002=1000000
C.Khó nhìn quá
D.362+262-52.36=362-2.36.26+262=(36-16)2=202=400
E.1052-25=(105-5)(105+5)=100.110=11000
F. 732-272=(73-27)(73+27)=46.100=4600
Bài 1 :
\(A=26^2-24^2=\left(26-24\right)\left(26+24\right)=2.50=100\)
\(B=27^2-25^2=\left(27-25\right)\left(27+25\right)=2.52=104\)
Vì \(100< 104\Rightarrow A< B\)
Bài 2 :
\(4\left(x+1\right)^2+\left(2x-1\right)^2-8\left(x-1\right)\left(x+1\right)=11\)
\(\Rightarrow4\left(x^2+2x+1\right)+4x^2-4x+1-8\left(x^2-1\right)=11\)
\(\Rightarrow4x^2+8x+4+4x^2-4x+1-8x^2+8=11\)
\(\Rightarrow4x=-2\)\(\Leftrightarrow x=-\frac{1}{2}\)
a, 25^2 - 15^2 = ( 25 - 15 )( 25 + 15) = 10 . 40 = 400
b, 87^2 + 73^2 - 27^2 - 13^2
= 87^2 - 27^2 + 73^2 - 13^2
= ( 87 - 27)( 87 + 27) + (73 - 13 )(73+ 13)
= 60 . 114 + 60 . 86
= 60( 114 + 86)
= 60 .200
= 12000
c, x^3 + 27 + 9 x^2 + 27x
= x^3 + 27x + 9x^2 + 27
=(x + 3)^3
thay x =97 ta có
= (97 + 3)^3
= 100^3
=1000000
d, 1,6^2 + 4.0,8.3,4 + 3,4^2 ( nè 3,4^2 chứ không phải 3,42)
= 1,6^2 + 2.2.0,8.3,4 + 3,4^2
=1,6^2 + 2.1,6.3,4 + 3,4^2
= (1,6 + 3,4)^2
= 5^2
= 25
e, x = 11 => 12 =x + 1 thay vào ta có
x^4 - ( x+ 1)x^3 + (x+1)x^2 -(x+1)x + 11
= x^4 - x^4 - x^13 + x^3 + x^2 - x^2 - x + 11
= -x + 11
= -11 + 11
= 0
ĐÚng ch o tui nha
\(a,=\left(73-27\right)\left(73^2+73\cdot27+27^2\right)=46\cdot8029=369334\\ b,=\left(63-27\right)\left(63+27\right)+\left(72-18\right)\left(72+18\right)\\ =100\cdot36+54\cdot100=100\left(36+54\right)=100\cdot90=9000\\ c,=\left(105-5\right)^3=100^3=1000000\)