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Answer:
Mình sửa lại đề, sai thì bạn bảo mình nhé!
a) \(25.6+5.5.29-45.5\)
\(=5.5.6+5.5.29-45.5\)
\(=5.30+5.145-45.5\)
\(=5.\left(30+145-45\right)\)
\(=5.130\)
\(=450\)
b) \(30.75+25.30-150\)
\(=30.\left(75+25\right)-150\)
\(=30.100-150\)
\(=3000-150\)
\(=2850\)
c) \(2.[\left(7-3^3:3^2\right):2^2+99]-100\)
\(=2.[\left(7-3\right):4+99]-100\)
\(=2.\left(1+99\right)-100\)
\(=200-100\)
\(=100\)
d) \(160-\left(4.25-3.23\right)\)
\(=160-\left(208-69\right)\)
\(=160-139\)
\(=21\)
e) \(\left(7^{2022}-7^{2021}\right):7^{2021}\)
\(=7^{2021}.\left(7-1\right):7^{2021}\)
\(=7-1\)
\(=6\)
g) \([36.4-4.\left(82-7.11\right).2]:4-2022^0\)
\(=[144-4.2.\left(82-77\right)]:4-1\)
\(=[144-8.5]:4-1\)
\(=104:4-1\)
\(=25\)
Tính toán lại cho mình vs ạ
Cho kĩ nha vì bài này để thi á
Ta có : \(3x^2y+5x^2+3y^2+5y=16\)
\(\Leftrightarrow3y\left(x^2+y\right)+5\left(x^2+y\right)=16\)
\(\Leftrightarrow\left(x^2+y\right)\left(3y+5\right)=16\)
a) Ta có A = -|x| + 2
= 2 - |x|
Lại có \(\left|x\right|\ge0\forall x\Rightarrow2-\left|x\right|\le2\forall x\)
Dấu "=" xảy ra khi x = 0
Vậy Max A = 2 <=> x = 0
b) Ta có B = -x2 + 5 = 5 - x2
Lại có \(x^2\ge0\forall x\Rightarrow5-x^2\le5\forall x\)
Dấu "=" xảy ra khi x2 = 0
=> x = 0
Vậy Max B = 5 <=> x = 0
c) Ta có : C = -|x + 1| + 12 = 12 - |x + 1|
Lại có \(\left|x+1\right|\ge0\forall x\Rightarrow12-\left|x+1\right|\le12\forall x\)
Dấu "=" xảy ra <=> x + 1 = 0
=> x = - 1
Vậy Max C = 12 <=> x = - 1
d) Ta có D = -2|x + 4| + 5 = 5 - 2|x + 4|
Lại có \(2\left|x+4\right|\ge0\forall x\Rightarrow5-2\left|x+4\right|\le5\forall x\)
Dấu "=" xảy ra <=> x + 4 = 0
=> x = - 4
Vậy Max D = 5 <=> x = -4
3/4 và 7/10
3/4=30/40 7/10=28/40
8/5vaf 7/20
8/5= 160/100 7/20=35/100
-5/14vaf 9/22
-5/14=-110/308 9/22=126/308
3/8và 5/27
3/8=81/216 5/27=40/216
còn lại tương tự
chúc bn học tốt
a) Vì AOB và BOC là 2 góc kề bù
=> AOB + BOC = 180o
=> AOB + 2. AOB = 180o
=> AOB. (1+ 2) = 180o
=> AOB. 3 = 180o
=> AOB = 180o : 3 = 60o
mà AOB + BOC = 180o
=> 60o + BOC = 180o
=> BOC = 180o- 60o = 120o
1, Ta có :
A = 1.2+2.3+3.4+4.5+...+100.101
B = 1.3+2.4+3.5+4.6+....+100.102
=> B - A = ( 1.2+2.3+3.4+4.5+...+100.101) - (1.3+2.4+3.5+4.6+...+100.102)
=> B - A = 1.2+2.3+3.4+4.5+...+100.101-1.3-2.4-3.5-4.6-....-100.102
=> B - A = 1.2+(2.3-1.3)+(3.4-2.4)+(4.5-3.5)+...+(100.101-99.101)-100.102
=> B - A = 2+3+4+5+...+101-10200
=> B - A = (2+101)+(3+100)+...+(51+52)-10200
=> B - A = 103+103+103+....+103-10200 ( 50 SỐ 103 )
=> B - A = 103.50-10200
=> B - A = 5150-10200
=> B - A = -5050
A = 1.2 + 2.3 + 3.4 + ... + 100.101
3A = 1.2.3 + 2.3.3 + 3.4.3 + ... + 100.101.3
3A = 1.2.3 + 2.3(4 - 1) + 3.4.(5 - 2) + ... + 100.101.(102 - 99)
3A = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + ... + 100.101.102 - 99.100.101
3A = 100.101.102
A = 34340
B = 1.2.3 + 2.3.4 + 3.4.5 + ... + 100.101.102
4B = 1.2.3.4 + 2.3.4.4 + 3.4.5.4 + ... + 100.101.102.4
4B = 1.2.3.4 + 2.3.4(5 - 1) + 3.4.5.(6-2) + ... + 100.101.102.(103 - 99)
4B = 1.2.3.4 + 2.3.4.5 - 1.2.3.4 + 3.4.5.6 - 2.3.4.5 + ... + 100.101.102.103 - 99.100.101.102
4B = 100.101.102.103
B = 26527650
Bài 3:
\(A=1.2+2.3+3.4+...+100.101\)
\(\Leftrightarrow3A=1.2.3+2.3.3+3.4.3+...+100.101.3\)
\(\Leftrightarrow3A=1.2.3+2.3\left(4-1\right)+3.4\left(5-2\right)+...+100.101\left(102-99\right)\)
\(\Leftrightarrow3A=1.2.3+2.3.4-1.2.3+3.4.5-2.3.4+...+100.101.102-99.100.101\)
\(\Leftrightarrow3A=\left(1.2.3-1.2.3\right)+...+\left(99.100.101-99.100.101\right)+100.101.102\)
\(\Leftrightarrow3A=100.101.102\)
\(\Leftrightarrow A=343400\)
\(B=1.2.3+2.3.4+3.4.5+...+100.101.102\)
\(\Leftrightarrow4B=1.2.3.4+2.3.4\left(5-1\right)+...+99.100.101\left(102-98\right)\)
\(\Leftrightarrow4B=1.2.3.4+2.3.4.5-1.2.3.4+...+99.100.101.102-98.99.100.101\)
\(\Leftrightarrow4B=99.100.101.102\)
\(\Leftrightarrow B=25497450\)
Bài 4:
\(A=714+382+286+318\)
\(\Leftrightarrow A=\left(714+286\right)+\left(382+318\right)\)
\(\Leftrightarrow A=1000+700=1700\)
\(B=25.34=35.86+65.75+65.45\)
\(\Leftrightarrow B=35.\left(34+86\right)+65.\left(75+25\right)\)
\(\Leftrightarrow B=35.120+65.100\)
\(\Leftrightarrow B=4200+6500=10700\)
\(C=\left(257.139-257.39\right):100\)
\(\Leftrightarrow C=257.\left(139-39\right):100\)
\(\Leftrightarrow C=257.100:100=257\)
\(D=102-96+90-84+...+54-48\)
\(\Leftrightarrow D=\left(102-72\right)+\left(-96+66\right)+\left(90-60\right)+\left(-84+54\right)+\left(78-48\right)\)
\(\Leftrightarrow D=30-30+30-30+30=30\)
Bổ sung bài 4:
\(E=3+5+7+...+2021\)
Số số hạng: \(\frac{2021-3}{2}+1=1010\)
Tổng: \(\frac{\left(3+2021\right).1010}{2}=1022120\)
\(A=1.2+2.3+3.4+...+2020.2021\)
\(\Leftrightarrow A=2+6+12+...+4082420\)
\(\Leftrightarrow A=2.6+6.2+12+...+4082420\)
\(\Leftrightarrow A=12+12+12+...+4082420\)
\(\Leftrightarrow A=4082420+12:2=2041216\)
\(\Leftrightarrow A=12.2041216\)
\(\Leftrightarrow A=24494592\)
\(B=1.2+2.3+3.4+...+n\left(n+1\right)\)
\(\Leftrightarrow3B=1.2.3+2.3.3+3.4.3+...+n\left(n+1\right).3\)
\(\Leftrightarrow3B=1.2\left(3-0\right)+2.3\left(4-1\right)+3.4\left(5-2\right)+...+n\left(n+1\right)[\left(n+2\right)-\left(n-1\right)]\)
\(\Leftrightarrow3B=1.2.3-0.1.2+2.3.4-1.2.3+2.3.4-2.3.4+...+n\left(n+1\right)\left(n+2\right)-\left(n-1\right).n\left(n+1\right)\)
\(\Leftrightarrow3B=n\left(n+1\right)\left(n+2\right)-0.1.2\)
\(\Leftrightarrow3B=n\left(n+1\right)\left(n+2\right)\)
\(\Leftrightarrow B=\frac{n\left(n+1\right)\left(n+2\right)}{3}\)