Giúp mik nah!!!
Bài 1:
1) (57+59).(68+610).(24-42)
2)9<3x<27
Bài 2:
Tìm x,y € N biết:
a)x.y-2x=0
b) (x-4).(x-3)=0
c)Chưng tỏ 3n+2+3n chia hết cho 10
a) – (- 12) + (+ 19) – (+12) + 8 - 19
b) (59 – 78) - (42 – 78 + 59)
c) (- 68 + 103) – (-50 – 68 + 103)
giúp mik voi ah, đag cần gấp
a, -(-12) + (+19) - (+12) + 8 - 19
= 12 + 19 - 12 + 8 - 19
= ( 12 - 12) + ( 19- 19) + 8
= 0 + 0 + 8
= 8
b, (59 - 78) - (42 - 78 + 59)
= 59 - 78 - 42 + 78 - 59
= (59 - 59) - 42 - ( 78 - 78)
= 0 - 42 - 0
= -42
c, ( - 68 + 103) - (-50 - 68 + 103)
= -68 + 103 + 50 + 68 - 103
= (-68 + 68) + ( 103 - 103) + 50
= 0 + 0 + 50
= 50
a) \(...=12+19-12+8-19=8\)
b) \(...=-19-23=-42\)
c) \(...=35-\left(-15\right)=35+15=50\)
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70=?
giúp mik trả lời câu hỏi này nha các bạn mik tích like nha
S=1+2+3-4-5-6+7+8+9-10-11-12+....+55+56+57-58-59-60
Bài 1: tính
e)45.(-24)+(-10).(-12)
f)(-41).(59+2)+59.(41-2)
g)(135-35).(-37)+37.(-42-58)
e. = - 1080 + 120
= -960
f. (-41) x 59 + ( -41).2 + 59 x 41 - 59 x 2
= 2 x ( -41 - 59 )
= 2 x ( -100)
= -200
g, ( 135 - 35 ) . ( -37 ) + 37 . ( -42 - 58 )
= 100 : ( -37 ) + 37 . -100
= 100 : ( -37 ) + ( 37 . -10 ) . -100
= 100 : ( -37 ) + ( -37 ) . -100
= ( -37 ) . ( 100 + -100 )
= ( -37 ) . 0
= 0
CHỨNG MINH : A =1/2*(1/6+1/24+1/60+...+1/9240) > 57/462
giúp mik giải bài này nhé
Xét riêng cái biểu thức trong ngoặc nhé, đặt là B :
B = 1/6+1/24+1/60+...+1/9240
B = 1/1x2x3+1/2x3x4+1/3x4x5+...+1/20x21x22
B = (1/1x2 - 1/2x3) : 2 + (1/2x3-1/3x4) : 2 + (1/3x4 - 1/4x5) : 2 +...+ (1/20x21 - 1/21x22) : 2
B = (1/1x2-1/2x3+1/2x3-1/3x4+1/3x4-...-1/21x22) : 2
B = (1/2 - 1/462) : 2
B = 115/462
=> A = 1/2 x 115/462 > 1/2 x 114/462 = 57/462 (đpcm)
tìm x hộ mik nah
5-8x-x^2=0
giúp mik nah mai nộp bài rồi
bam may tinh
hoac tính \(\Delta\)
roi ra x=-4+can(21)
x=-4-can(21)
Bài 1: Tìm x là STN biết:
1/ 5x - 2 - 32 = 24 - ( 68 : 66 - 62)
2/ 3x + 42 = 196 : (193 x 192) - 3.12014
3/ 2x + 2x + 4 = 272
4/ 3 + 2x - 1 = 24 - \([4^2-(2^2-1)]\)
1: =>\(5^{x-2}-9=2^4-\left(6^2-6^2\right)\)
=>\(5^{x-2}=16+9=25\)
=>x-2=2
=>x=4
2: \(\Leftrightarrow3^x+16=19^6:19^5-3=19-3=16\)
=>3^x=0
=>x=0
3: \(\Leftrightarrow2^x+2^x\cdot16=272\)
=>2^x*17=272
=>2^x=16
=>x=4
4: \(\Leftrightarrow2^{x-1}+3=24-\left(4^2-2^2+1\right)=24-\left(16-4+1\right)\)
=>\(2^{x-1}+3=24-16+4-1=8+4-1=12-1=11\)
=>2^x-1=8
=>x-1=3
=>x=4
Bài 1
3580 : 32 =
1654 : 24 =
9870 : 42 =
598 : 68 =
1435 : 13 =
3580 : 32 = 111,875
1654 : 24 = 68,92
9870 : 42 = 235
598 : 68 = 8,79
1435 : 13 = 110,38
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