3 mũ 3+4mũ 3+5 mũ 3+.......+(x+1)tất cả mũ 3=6075
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a.(3^2+4^2).x=10^2
(9+16).x =100
25.x =100
x =100:25
x =4
b.(x-5)^2 =81
x-5 =9
x =9+5
x =14
c.(2x+1)^3 = 343
2x+1 = 7
2x =7-1
2x =6
x =6:2
x = 3
(5 mũ 2)mũ 3 : 5 mũ 2
5 mũ 2 x3 :5 mũ 2
5 mũ 6 : 5 mũ 2 =5 mũ 4=625
a, \(\left(x+\frac{4}{3}y^2\right)^2\)
\(=x^2+\frac{8}{3}xy^2+\frac{16}{9}y^4\)
b, \(\left(2x-3y\right)^2\)
\(=4x^2-12xy+9y^2\)
c, \(\left(x^2+2x\right)\left(2x-x^2\right)\)
\(=\left(2x+x^2\right)\left(2x-x^2\right)\)
\(=4x^2-x^4\)
d, \(\left(x+\frac{1}{2}\right)^3\)
\(=x^3+\frac{3}{2}x^2+\frac{3}{4}x+\frac{1}{8}\)
e, \(\left(2x-\frac{6}{5}y\right)^3\)
\(=8x^3-\frac{72}{5}x^2y+\frac{216}{25}xy^2-\frac{216}{125}y^3\)
Bài 6 :
a) \(\dfrac{625}{5^n}=5\Rightarrow\dfrac{5^4}{5^n}=5\Rightarrow5^{4-n}=5^1\Rightarrow4-n=1\Rightarrow n=3\)
b) \(\dfrac{\left(-3\right)^n}{27}=-9\Rightarrow\dfrac{\left(-3\right)^n}{\left(-3\right)^3}=\left(-3\right)^2\Rightarrow\left(-3\right)^{n-3}=\left(-3\right)^2\Rightarrow n-3=2\Rightarrow n=5\)
c) \(3^n.2^n=36\Rightarrow\left(2.3\right)^n=6^2\Rightarrow\left(6\right)^n=6^2\Rightarrow n=6\)
d) \(25^{2n}:5^n=125^2\Rightarrow\left(5^2\right)^{2n}:5^n=\left(5^3\right)^2\Rightarrow5^{4n}:5^n=5^6\Rightarrow\Rightarrow5^{3n}=5^6\Rightarrow3n=6\Rightarrow n=3\)
Bài 7 :
a) \(3^x+3^{x+2}=9^{17}+27^{12}\)
\(\Rightarrow3^x\left(1+3^2\right)=\left(3^2\right)^{17}+\left(3^3\right)^{12}\)
\(\Rightarrow10.3^x=3^{34}+3^{36}\)
\(\Rightarrow10.3^x=3^{34}\left(1+3^2\right)=10.3^{34}\)
\(\Rightarrow3^x=3^{34}\Rightarrow x=34\)
b) \(5^{x+1}-5^x=100.25^{29}\Rightarrow5^x\left(5-1\right)=4.5^2.\left(5^2\right)^{29}\)
\(\Rightarrow4.5^x=4.25^{2.29+2}=4.5^{60}\)
\(\Rightarrow5^x=5^{60}\Rightarrow x=60\)
c) Bài C bạn xem lại đề
d) \(\dfrac{3}{2.4^x}+\dfrac{5}{3.4^{x+2}}=\dfrac{3}{2.4^8}+\dfrac{5}{3.4^{10}}\)
\(\Rightarrow\dfrac{3}{2.4^x}-\dfrac{3}{2.4^8}+\dfrac{5}{3.4^{x+2}}-\dfrac{5}{3.4^{10}}=0\)
\(\Rightarrow\dfrac{3}{2}\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)+\dfrac{5}{3.4^2}\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)=0\)
\(\Rightarrow\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)\left(\dfrac{3}{2}+\dfrac{5}{3.4^2}\right)=0\)
\(\Rightarrow\dfrac{1}{4^x}-\dfrac{1}{4^8}=0\)
\(\Rightarrow\dfrac{4^8-4^x}{4^{x+8}}=0\Rightarrow4^8-4^x=0\left(4^{x+8}>0\right)\Rightarrow4^x=4^8\Rightarrow x=8\)
a) 1810 : 310 = (2.32)10 : 310 = 210 . 320 : 310 = 210 . 310 = 610
b) 276 : 9 = (33)6 : 9 = 318 : 32 = 318-2 = 316
c) Thiếu dữ liệu đề bài
d) 225 : 324 = 225 : (25)4 = 225 : 220 = 25
Bài 2 : 5.x2 = 245 => x2 = 245:5 = 49 => x = \(\pm\)7
1) + S = 5 + 52 + 53 + ... + 596 (có 96 số; 96 chia hết cho 6)
S = (5 + 52 + 53 + 54 + 55 + 56) + (57 + 58 + 59 + 510 + 511 + 512) + ... + (591 + 592 + 593 + 594 + 595 + 596)
S = (5 + 54) + (52 + 55) + (53 + 56) + (57 + 510) + ... + (593 + 596)
S = 5.(1 + 53) + 52.(1 + 52) + 53.(1 + 53) + 57.(1 + 53) + ... + 593.(1 + 53)
S = 5.126 + 52.126 + 53.126 + 57.126 + ... + 593.126
S = 126.(5 + 52 + 53 + 57 + ... + 593) chia hết cho 126
+ Do 5 + 52 + 53 + 57 + ... + 593 chia hết cho 5 mà 126 chia hết cho 2
=> S chia hết cho 10 => S có tận cùng là 0
2) 162008 - 82000
= (...6) - (84)500
= (...6) - (...6)500
= (...6) - (...6)
= (...0) chia hết cho 10
3) 13 + 23 + 33 + 43 + 53 + 63 + 73 + 83 + 93 + 103 = (x + 12)2
=> 1 + 8 + 27 + 64 + 125 + 216 + 343 + 512 + 729 + 1000 = (x + 1)2
=> (1 + 729) + (8 + 512) + (27 + 343) + (64 + 216) + 125 + 1000 = (x + 1)2
=> 730 + 520 + 370 + 280 + 1125 = (x + 1)2
=> (730 + 370) + (520 + 280) + 1125 = (x + 1)2
=> 1100 + 800 + 1125 = (x + 1)2
=> 3025 = (x + 1)2, vô lí
1) + S = 5 + 52 + 53 + ... + 596 (có 96 số; 96 chia hết cho 6)
S = (5 + 52 + 53 + 54 + 55 + 56) + (57 + 58 + 59 + 510 + 511 + 512) + ... + (591 + 592 + 593 + 594 + 595 + 596)
S = (5 + 54) + (52 + 55) + (53 + 56) + (57 + 510) + ... + (593 + 596)
S = 5.(1 + 53) + 52.(1 + 52) + 53.(1 + 53) + 57.(1 + 53) + ... + 593.(1 + 53)
S = 5.126 + 52.126 + 53.126 + 57.126 + ... + 593.126
S = 126.(5 + 52 + 53 + 57 + ... + 593) chia hết cho 126
+ Do 5 + 52 + 53 + 57 + ... + 593 chia hết cho 5 mà 126 chia hết cho 2
=> S chia hết cho 10 => S có tận cùng là 0