45. C

46. B

48. D

49. B

ĐKXĐ: \(x\ne0;y\ne0\)

\(\sqrt[3]{8a^3}-4a=2a-4a=-2a\)

Đúng nhé.

\(x=-4\)

Bài 6: 

a/ \(x\in\left\{-2;-1\right\}\)

b/ \(x\in\left\{-4;-3;-2\right\}\)

c/ \(x\in\left\{-5;-4\right\}\)

d/ \(x\in\left\{-1;0;1;2;3\right\}\)

e/ \(x\in\left\{7,8,9\right\}\)

g/ \(x\in\left\{-6;-5;-4;-3;-2;-1\right\}\)

Bài 7: 

a/ \(-26+\left(-32\right)=-\left(26+32\right)=-58\)

b/ \(-267+\left(-473\right)=-\left(267+473\right)=-740\)

c/ \(27+\left(-43\right)=-\left(43-27\right)=-16\)

d/ \(126+\left(-34\right)=126-34=92\)

e/ \(81+\left(-25\right)=81-25=56\)

g/ \(-92+\left(-62\right)=-\left(92+62\right)=-154\)

h/ \(-125+\left(-175\right)=-\left(125+175\right)=-300\)

i/ \(-34+\left(-26\right)=-\left(34+26\right)=-60\)

k/ \(-156+84=-\left(156-84\right)=-72\)

2. Nam used to swim when he was a child.

Đề bài không có điểm M bạn ơi. Bạn kiểm tra lại nhé.

B

\(16x+40=10.3^2+4+5\left(1+2+3\right)\)

\(16x+40=10.9+4+5.6\)

\(16x+40=90+4+30\)

\(16x+40=124\)

\(16x=124-40\)

\(16x=84\)

\(x=\dfrac{84}{16}=4\)