Câu 1: Tính:
1) 49 : 7\(^x\) = 2401
2) 25 : 5\(^x\) = 5\(^x\)
Tìm số tự nhiên x , biết:
1) 49 . 7\(^x\) = 2401
2) 25 : 5\(^x\) = 5\(^x\)
49 . 7x = 2401
=> 72 . 7x = 74
7x = 74 : 72
7x = 72
=> x = 2
2) 25 : 5x = 5x
VD : 5x : 5x = 1
=> 25 : 5 = 5
=> 25 : 51 = 51
=> x = 1
1) 49 . 7x = 2401
7x = 2401 : 49
7x = 49
=> 7x = 72
=> x = 2
Vậy x = 2
2) 25 : 5x = 5x
=> 52 = 5x . 5x
=> 52 = 5x + x
=> 2 = x + x
=> 2 = 2x
=> x = 2 : 2
=> x = 1
Vậy x = 1
Chúc bạn học tốt!
\(a\))\(49.7^x\)\(=2401\)
\(\Rightarrow\) \(7^x\)\(=2401\div49\)
\(\Rightarrow\)\(7^x\) \(=49\)
\(\Leftrightarrow\) \(7^x\)\(=7^2\)
\(\Rightarrow\) \(x=2\)
\(b\)) \(25\div5^x\) \(=5^x\)
\(\Leftrightarrow5^2\) \(\div5^x\) \(=5^x\)
\(\Rightarrow\) \(5^2\) \(=5^x\)\(.5^x\)
\(\Rightarrow\) \(2=x+x\)
\(\Leftrightarrow\) \(2=2x\)
\(\Rightarrow\) \(x=2\div2\)
\(\Rightarrow\) \(x=1\)
bài 1 : Tìm x
a) 5 + ( x + 27 ) = 64
b) 64 - ( x - 2 ) = 25
c) 7 - ( x + 5 ) + 14 = 343
d) 5 . x - 25 = 10
e) 4 . ( x - 5 ) - 8 = 48
f) 49 - ( 15 + x ) = 12
g) 49 - 7. ( 13 - x ) = 14
h) 155 - 10. ( x + 1 ) = 55
5 + ( x + 27 ) = 64
( x + 27 ) = 64 - 5 ( x + 27 ) = 59 x = 59 - 27 x = 32a) \(\Rightarrow x+27=59\Rightarrow x=32\)
b) \(\Rightarrow x-2=39\Rightarrow x=41\)
c) \(\Rightarrow x+5=-322\Rightarrow x=-327\)
d) \(\Rightarrow5x=35\Rightarrow x=7\)
e) \(\Rightarrow4\left(x-5\right)=56\Rightarrow x-5=14\Rightarrow x=19\)
f) \(\Rightarrow15+x=37\Rightarrow x=22\)
g) \(\Rightarrow7\left(13-x\right)=35\Rightarrow13-x=5\Rightarrow x=8\)
h) \(\Rightarrow10\left(x+1\right)=100\Rightarrow x+1=10\Rightarrow x=9\)
1,Tính nhanh
a, 568 + 568 x 135 - 568 x 36
b, 17 x 49 + 49 x 37 + 54 x 26 + 54 x 25
c, 14 x 35 x 5 + 10 x 25 x 7 + 20 x 70
a, 568 + 568 x 135 - 568 x 36
= 568 x ( 1 + 135 - 36)
= 568 x 100
56 800
b, 17 x 49 + 49 x 37 + 54 x 26 + 54 x 25
= 49 x ( 17 + 37) + 54 x ( 26 + 25 )
= 49 x 54 + 54 x 51
= 54 x ( 49 + 51)
= 54 x 100
= 5 400
c, 14 x 35 x 5 + 10 x 25 x 7 + 20 x 70
= ( 2 x 35) x ( 7 x 5) + ( 10 x 7) x 25 + 20 x 70
= 70 x 35 + 70 x 25 + 20 x 70
= 70 x ( 35 + 25 + 20)
= 70 x 80
= 5 600
a) 568 + 568 x 135 - 568 x 36
= 568 x ( 1+1+135-1-36 )
=568 x 100
=5680
b) 17 x 49 + 49 x 37 + 54 x 26 + 54 x 25
= 49 x ( 17 + 37 ) + 54 x ( 26 + 25 )
= 49 x 54 + 54 x 51
= 54 x ( 49 + 51 )
= 54 x 100
= 5400
c) 14 x 35 x 5 + 10 x 25 x 7 + 20 x 70
= 70 x 35 + 10 x 25 x 7+ 20 x 70
= 70 x 35 + 250 x 7 + 20 x 70
= 70 x 35 + 70 x 25 + 20 x 70
= 70 x (35+25+20)
= 70 x 80
= 5600
Tìm x thuộc Z, biết: 1. 2 |x - 1| - 5(x + 3) - 2(x-7) = |x - 1|- 7x 2. |x - 2| - 5(x - 4) =20 - 5x 3. 4(x - 2) - 3(x + 4 =(-4)(+3)(-125)(+25)(-8) 4. -3(2x - 4) + 7(x-5) = (-67)(1-301) - 301 . 67 5. 7(x - 5) - 4(x+3) = 2(x - 5)+ (13-135 + 49 ) - (13+49) 6. 5(x-3) - 2(x + 1)= 3 + 2(x-1)+(18 + 29) +( 185 - 18 - 29)
Câu 1 Tính :
a) (-1/4+7/33-5/3)-(-15/12+6/11-48/49)
b)167*54-167*55/167*252-167*55
Câu 2) tìm giá trị lớn nhất của A = 12- |x+4|
Tính nhẩm:
7 x 8 = ..... 16 : 2 = ..... 36 : 6 = ..... 49 : 7 = .....
2 x 5 = ..... 72 : 8 = ..... 9 x 3 = ...... 63 : 7 = .....
6 x 4 = ..... 25 : 5 = ..... 4 x 8 = ...... 7 x 5 = ......
7 x 8 = 56 16 : 2 = 8 36 : 6 = 6 49 : 7 = 7
2 x 5 = 10 72 : 8 = 9 9 x 3 = 27 63 : 7 = 9
6 x 4 = 24 25 : 5 = 5 4 x 8 = 32 7 x 5 = 35
7 x 8 = 56
2 x 5 = 10
6 x 4 = 24
16 : 2 = 8
72 : 8 = 9
25 : 5 = 5
36 : 6 = 6
9 x 3 = 27
4 x 8 = 32
49 : 7 = 7
63 : 7 = 9
7 x 5 = 35
Tìm các số nguyên x , sao cho :
a) (x^2+5)×(x^2-25)=0
b) ( x^2-5) ( x^2-25)<0
c) (x-2)×( x+1)=0
d) ( x^2+7)× ( x^2-49)<0
e) ( x^2-7) × ( x^2-49) <0
đăng kí hộ
https://www.youtube.com/channel/UCT23clmdY5azigRNMRDxGfw
a) \(\left(x^2+5\right).\left(x^2-25\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x^2+5=0\\x^2-25=0\end{cases}\Rightarrow\orbr{\begin{cases}x^2=-5\left(vl\right)\\x^2=25\end{cases}\Rightarrow}\orbr{\begin{cases}\\x=\pm5\end{cases}}}\)
b) \(\left(x^2-5\right)\left(x^2-25\right)< 0\)
\(\Rightarrow\left(x^2-5\right)\)và \(\left(x^2-25\right)\)trái dấu
Vì \(\left(x^2-5\right)>\left(x^2-25\right)\)
\(\Rightarrow\hept{\begin{cases}x^2-5>0\\x^2-25< 25\end{cases}\Rightarrow\hept{\begin{cases}x^2>5\\x^2< 50\end{cases}}}\)
\(\Rightarrow5< x^2< 50\)
\(\Rightarrow x^2\in\left\{0;1;4;9;16;25;36;49\right\}\)
\(\Rightarrow x\in\left\{0;\pm1;\pm2;\pm3;\pm4;\pm5;\pm6;\pm7\right\}\)
c) \(\left(x-2\right)\left(x+1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-2=0\\x+1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=2\\x=-1\end{cases}}}\)
các câu còn lại lm tương tự nhé!! hok tốt!!
1.Tìm x thuộc Z:
a) (x-2)(x+1)=0
b) (x^2 +7).(x^2 -49)<0
c) (x^2 -7).(x^2 -49)<0
2. Tính, tính hợp lí:
a) (-55).(-25).(-8)
b) (-1).(-2).(-3).(-4).(-5).10
c) (-1).(-2)-(-3).(-4).(-2).(-3)
d) (-2).(-3):(-1)-(-3):(-6)+(-2)
1a) (x-2)(x+1)= 0
Suy ra \(\orbr{\begin{cases}x-2=0\\x+1=0\end{cases}}\)Suy ra \(\orbr{\begin{cases}x=2\\x=-1\end{cases}}\)
5) 6x – 5 = 3 + 4x 6) x – (17 – x) = x – 7
7) 9 – 25 = (7 – x) – ( 25 + 7) 8) 10 – 2.(4 – 3x) = - 4
9) (-12)2
.x = 56 + 10. 13x 10) 2x2
– 1 = 49