a)
\(5^6:5^4+3^2-2021^0=5^2+3^2-1=25+9-1=33\)
b)
\(100-\left[60-\left(9-2^3\right).34\right].2=100-\left[60-\left(9-8\right).34\right].2\)
\(=100-\left(60-1.34\right).2=100-\left(60-34\right).2=100-26.2=100-52=48\)

B
B

đâu có làm tắt đâu
kiến thức 2 góc trong cùng phía bù nhau thì chỉ cần 1 dòng là đc mà
 

a)
\(\sqrt{\left(x-4\right)^2}=2x+7\)
TH1 \(x\ge4\)
=>x-4 = 2x+7
-x=11
x=-11 ( không thỏa mãn )
TH2
x<4
=> -x+4=2x+7
=> -3x=3
=>x=-1
b)
\(5-\sqrt{\left(x-1\right)^2}=0\)
\(-\left|x-1\right|=-5\)
\(\left|x-1\right|=5\)
TH1  x\(\ge1\)
x-1=5
x=6
TH2 x<1
-x+1=5
-x=4
x=-4(ko thỏa mãn)

2 . 53 . 27 + 6 . 9 . 87 - 3 . 18 . 40 
= 2. 53 . 9 . 3 + 2. 3 .9 .87 - 3 .2 .9 .40
= 54.53+54.87-54.40
=54(53+87-40)
=54. 100=5400

12 . 25 + 29 . 25 + 59 . 25 
= 25 . ( 12+29+59)
=25 . 90
=2250

43 . 37 + 93 . 43 + 57 . 61 + 69 . 57 
= 43.(37+93)+57(61+69)
=43.130+57.130
=130.(43+57)
=130.100
=13 000

12 . 53 + 53 . 172 - 53 
=53(12+172-1)
=53.184
=9752

35 . 54 + 35 . 58 + 65 . 75 + 65 . 45 
=35(54+58)+65(75+45)
=35.112+65.120
=3920+7800
=11720

39 . 8 + 70 . 3 + 31 . 8 
=8(39+31)+70.3
=8.70+70.3
=70.(8+3)
=70.11
=770

bài 1
a)
=(x+y-x+y)(x+y+x-y)
=2x.2y
=4xy
b)
B=(x+y-x+y)²=4y²
c)
=(x+y-x+y)[(x+y)²+(x+y)(x-y)+(x-y)²]-2y³
=2y(\(x^2+2xy+y^2+x^2-y^2+x^2-2xy+y^2\))-2y³
=\(2y\left(3x^2+y^2\right)-2y^3=6x^2y+2y^3-2y^3=6x^2y\)

bài 5
góc BAb=180⁰-120⁰=60⁰
mà B1=góc BAb=60⁰(so le trong)
bài 7
có góc BDC=180⁰- góc BDb=180⁰-150⁰=30⁰
=>góc BDC= góc aBD
=>a//b
=>A1=góc ACD=70⁰
=>A2=180⁰-ACD=180⁰-70⁰=110⁰

A4=180⁰-A1=180⁰-60⁰=120⁰
A1=B3(so le trong)
mà B3=B1(đối đỉnh)
=>A1=B1=60⁰
=>A1=B3=60⁰

A mấy = 60 kia

\(A=\dfrac{x^3\left(x+1\right)+\left(x+1\right)}{x^2\left(x+1\right)-\left(x+1\right)}=\dfrac{\left(x^3+1\right)\left(x+1\right)}{\left(x^2-1\right)\left(x+1\right)}\)
\(=\dfrac{x^3+1}{x^2-1}=\dfrac{\left(x+1\right)\left(x^2-x+1\right)}{\left(x+1\right)\left(x-1\right)}=\dfrac{x^2-x+1}{x-1}\)