2.(13 - 4.9 + 16)

= 2.(13 - 36 + 16)

= 2.[ 13 - (36 - 16)]

= 2.[13 - 20]

= 2.(-7)

= -14 

lừa thôi 

a) 127 - 2(-2x + 4)² = -1

2(-2x + 4)² = 127 + 1

2(-2x + 4)² = 128

(-2x + 4)² = 128 : 2

(-2x + 4)² = 64

-2x + 4 = 8 hoặc -2x + 4 = -8

*) -2x + 4 = 8

-2x = 8 - 4

-2x = 4

x = 4 : (-2)

x = -2

*) -2x + 4 = -8

-2x = -8 - 4

-2x = -12

x = -12 : (-2)

x = 6

b) -6² - 3.(-4 - x)³ = -39

3(-4 - x)³ = -6² + 39

3(-4 - x)³ = -36 + 39

3(-4 - x)³ = 3

(-4 - x)³ = 3 : 3

(-4 - x)³ = 1

(-4 - x)³ = 1³

-4 - x = 1

x = -4 - 1

x = -5

c) (-7x - 35).(2x² - 32) = 0

-7x - 35 = 0 hoặc 2x² - 32 = 0

*) -7x - 35 = 0

-7x = 0 + 35

-7x = 35

x = 35 : (-7)

x = -5

*) 2x² - 32 = 0

2x² = 0 + 32

2x² = 32

x² = 32 : 2

x² = 16

x = -4; x = 4

Vậy x = -5; x = -4; x = 4

d) (2018 + 2x)(4x² + 8) = 0

2018 + 2x = 0 (do 4x² + 8 > 0)

2x = 0 - 2018

2x = -2018

x = -2018 : 2

x = -1014

e) -145 - 4(3 - 2x)² = -245

4(3 - 2x) = -145 + 245

4(3 - 2x) = 100

3 - 2x = 100 : 4

3 - 2x = 25

2x = 3 - 25

2x = -22

x = -22 : 2

x = -11

g) 4(-x + 1)³ - (-5)² = -525

4(-x + 1)³ - 25 = -525

4(-x + 1)³ = -525 + 25

4(-x + 1)³ = -500

(-x + 1)³ = -500 : 4

(-x + 1)³ = -125

(-x + 1)³ = (-5)³

-x + 1 = -5

-x = -5 - 1

-x = -6

x = 6

chị giúp em đc mấy câu hỏi trước đc ko  ạ? 

           6n - 5 ⋮ 2n + 1

3.(2n + 1) - 8 ⋮ 2n + 1

                  8 ⋮ 2n + 1

2n + 1  \(\in\) Ư(8) = {-8; -4; -2; -1; 1; 2; 4; 8}

n \(\in\) { - \(\dfrac{9}{2}\); - \(\dfrac{5}{2}\); -\(\dfrac{3}{2}\); 0;-1; \(\dfrac{1}{2}\); \(\dfrac{3}{2}\); \(\dfrac{7}{2}\)}

\(A=2+2^2+2^3+...+2^{2024}\)

\(=\left(2+2^2+2^3+2^4\right)+\left(2^5+2^6+2^7+2^8\right)+...+\left(2^{2021}+2^{2022}+2^{2023}+2^{2024}\right)\)

\(=\left(2+2^2+2^3+2^4\right)+2^4\left(2+2^2+2^3+2^4\right)+...+2^{2020}\left(2+2^2+2^3+2^4\right)\)

\(=30\left(1+2^4+...+2^{2020}\right)⋮10\)

=>Chữ số hàng đơn vị của A là 0

Lời giải:

$A=(2+2^2+2^3+2^4)+(2^5+2^6+2^7+2^8)+....+(2^{2021}+2^{2022}+2^{2023}+2^{2024})$

$=2(1+2+2^2+2^3)+2^5(1+2+2^2+2^3)+....+2^{2021}(1+2+2^2+2^3)$

$=(1+2+2^2+2^3)(2+2^5+...+2^{2021})$

$=15(2+2^5+...+2^{2021})\vdots 15\vdots 5$

Hiển nhiên $A$ cũng chia hết cho 2

$\Rightarrow A\vdots 2; 5\Rightarrow A\vdots 10$

$\Rightarrow A$ tận cùng là $0$

h: \(\left(-145\right)-5\left(2x-1\right)^3=480\)

=>\(5\left(2x-1\right)^3=-145-480\)=-625

=>(2x-1)³=-125

=>2x-1=-5

=>2x=-5+1=-4

=>x=-4/2=-2

k: \(3\left(-4+x\right)^3-\left(-4\right)^2=-97\)

=>\(3\left(x-4\right)^3-16=-97\)

=>\(3\cdot\left(x-4\right)^3=-97+16=-81\)

=>\(\left(x-4\right)^3=-27\)

=>x-4=-3

=>x=-3+4=1

n: \(195+3\left(-2x+5\right)^3=192\)

=>\(3\left(-2x+5\right)^3=192-195=-3\)

=>\(\left(-2x+5\right)^3=-1\)

=>-2x+5=-1

=>-2x=-1-5=-6

=>\(x=\dfrac{-6}{-2}=3\)

o: \(\left(-148\right)-5\left(-x+6\right)^4=-228\)

=>\(148+5\left(x-6\right)^4=228\)

=>\(5\left(x-6\right)^4=80\)

=>\(\left(x-6\right)^4=16\)

=>\(\left[{}\begin{matrix}x-6=2\\x-6=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=4\end{matrix}\right.\)

p: \(-43-\left(-4+x\right)^4=-44\)

=>\(\left(x-4\right)^4+43=44\)

=>\(\left(x-4\right)^4=1\)

=>\(\left[{}\begin{matrix}x-4=1\\x-4=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\end{matrix}\right.\)

q: \(3\left(-x+5\right)^2-\left(-5\right)^2\cdot\left(-2\right)^3=203\)

=>\(3\left(x-5\right)^2-25\cdot\left(-8\right)=203\)

=>\(3\left(x-5\right)^2+200=203\)

=>\(3\left(x-5\right)^2=3\)

=>(x-5)²=1

=>\(\left[{}\begin{matrix}x-5=1\\x-5=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=4\end{matrix}\right.\)

h.

$(-145)-5(2x-1)^3=480$

$5(2x-1)^3=-145-480=-625$

$(2x-1)^3=-625:5=-125=(-5)^3$

$\Rightarrow 2x-1=-5$

$\Rightarrow x=-3$

k.

$3(-4+x)^3-(-4)^2=-97$

$3(-4+x)^3-16=-97$

$3(-4+x)^3=-97+16=-81$

$(-4+x)^3=-81:3=-27=(-3)^3$

$\Rightarrow -4+x=-3$

$\Rightarrow x=-3-(-4)=1$

a)17.85+15.17+(-120)

=17.(85+15)+(-120)

=17.100+(-120)

=1700+(-120)

=1580

a: \(17\cdot85+15\cdot17+\left(-120\right)\)

\(=17\left(85+15\right)-120\)

\(=17\cdot100-120=1700-120=1580\)

b: \(75-\left(-3\cdot5^2+4\cdot2^3\right)\)

\(=75+3\cdot5^2-4\cdot2^3\)

\(=75+3\cdot25-4\cdot8\)

\(=75+75-32=150-32=118\)

c: \(75-\left(3\cdot5^2-4\cdot2^3\right)\)

\(=75-3\cdot25+4\cdot8\)

\(=75-75+32=32\)

d: \(\left(-15\right)+14+\left(-85\right)\)

\(=\left(-15-85\right)+14\)

=-100+14

=-86

e: \(28\cdot76+28\cdot24\)

\(=28\left(76+24\right)\)

\(=28\cdot100=2800\)

f: \(29\left(19-13\right)-19\left(29-13\right)\)

\(=29\cdot19-29\cdot13-19\cdot29+19\cdot13\)

\(=-29\cdot13+19\cdot13\)

\(=13\left(-29+19\right)=13\cdot\left(-10\right)=-130\)

Lời giải:

b. $-138-3(2x^2-1)=-169$

$3(2x^2-1)=-148-(-169)=21$

$2x^2-1=21:3=7$

$2x^2=7+1=8$

$x^2=4=2^2=(-2)^2\Rightarrow x=\pm 2$

c.

$4(-x+5)^2-15=21$

$4(-x+5)^2=21+15=36$

$(-x+5)^2=36:4=9=3^2=(-3)^2$

$\Rightarrow -x+5=3$ hoặc $-x+5=-3$

$\Rightarrow x=2$ hoặc $x=8$

d.

$4(-3x^2-145)=-628$

$-3x^2-145=-628:4=-157$

$3x^2+145=157$

$3x^2=157-145=12$

$x^2=12:3=4=2^2=(-2)^2$

$\Rightarrow x=\pm 2$
e.

$252-3(-x-5)^2=225$

$3(-x-5)^2=252-225=27$

$(-x-5)^2=27:3=9$

$(x+5)^2=3^2=(-3)^2$

$\Rightarrow x+5=3$ hoặc $x+5=-3$

$\Rightarrow x=-2$ hoặc $x=-8$

e: \(\left(-4156+2021\right)-\left(119+2021-4156\right)\)

\(=-4156+2021-119-2021+4156\)

\(=\left(-4156+4156\right)+\left(2021-2021\right)-119\)

=0+0-119

=-119

g: \(315\cdot75-\left(15\cdot100-315\cdot25\right)\)

\(=315\cdot75-15\cdot100+315\cdot25\)

\(=315\left(75+25\right)-15\cdot100\)

\(=315\cdot100-15\cdot100=300\cdot100=30000\)

h: \(\left(-489\right)\cdot125-\left(125\cdot11-500\cdot25\right)\)

\(=-489\cdot125-125\cdot11+500\cdot25\)

\(=125\left(-489-11\right)+500\cdot25\)

\(=125\cdot\left(-500\right)+500\cdot25\)

\(=500\left(-125+25\right)\)

\(=500\cdot\left(-100\right)=-50000\)

Bài 2:

a: \(-415-3\left(2x-1\right)^2=-490\)

=>\(3\left(2x-1\right)^2+415=490\)

=>\(3\left(2x-1\right)^2=75\)

=>\(\left(2x-1\right)^2=25\)

=>\(\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=6\\2x=-4\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

Câu 7: B

Câu 8: D

a: \(\left(-256\right)\cdot45-256\cdot56+256\)

\(=256\left(-45-56+1\right)\)

\(=256\left(-100\right)=-25600\)

b: \(\left(-2\right)^3\cdot1975\cdot\left(-4\right)\cdot\left(-5\right)^3\cdot25\)

\(=\left(-8\right)\cdot\left(-125\right)\cdot\left(-4\right)\cdot25\cdot1975\)

\(=1000\cdot\left(-100\right)\cdot1975=-197500000\)

c: \(2076-1976\cdot65-1976\cdot35\)

\(=2076-1976\left(65+35\right)\)

\(=2076-1976\cdot100=2076-197600=-195524\)

d: \(-437-25\cdot78+25\cdot178\)

\(=-437+25\left(178-78\right)\)

\(=-437+2500=2063\)