5.42 - 18:32 = 5.16 – 18:9 = 80 - 2 = 78

\(98.42-50\left[\left(18-2^3\right):2+3^2\right]\\ =4116-50\left[\left(18-8\right):2+9\right]\\ =4116-50\left[10:2+9\right]\\ =4116-50\left[5+9\right]\\ =4116-50.14\\ =4116-700\\ =3416\)

98.42-50.[(18-2³):2 +3²]

=98.42-50.[(18-8):2+3²]

=98.42-50.[10:2+3]

=98.42-50.[5+3]

=98.42-50.8

= 4116-400

=3716

=98*42-50*[(18-8):2+9]

=98*42-50*14

=3416

\(a.\sqrt{\left(\sqrt{2}-\sqrt{3}\right)^2}+\sqrt{18}=\left|\sqrt{2}-\sqrt{3}\right|+3\sqrt{2}=\sqrt{3}-\sqrt{2}+3\sqrt{2}\left(\sqrt{3}>\sqrt{2}\right)=\sqrt{3}+2\sqrt{2}\)\(b.3\sqrt{2}-4\sqrt{18}+2\sqrt{32}-\sqrt{50}=3\sqrt{2}-12\sqrt{2}+8\sqrt{2}-5\sqrt{2}=-6\sqrt{2}\)

a: \(=\sqrt{3}-\sqrt{2}+3\sqrt{2}=2\sqrt{2}+\sqrt{3}\)

a)\(\left(-3\right).8.\left(-2\right).5=\left(-3\right).\left(-2\right).8.5\)

                                          \(=6.40=240\)

b)\(127-18.\left(5+6\right)=127-18.11\)

                                             \(=127-198=-71\)

c)\(125-\left(-75\right)+32-\left(48+32\right)=125+75+32-48-32\)

                                                                              \(\left(125+75\right)+\left(32-32\right)-48=200-48=152\)

d)\(3.\left(-4\right).2+2.\left(-5\right)-20=-12.2+2.\left(-5\right)-20\)

                                                             \(=\left(-12-5\right).2-20=-17.2-20=-140-20=-160\)

Chúc bạn học tốt

(-1)+-39/13

Câu 12: B

Câu 13: C

Câu 14: A

C12 B

C13 C

C14 A

12.B     13. C         14.  A

5.42 – 18 : 32

= 5.16 – 18 : 9 = 80 – 2 = 78

Phân tích ra thừa số nguyên tố: 78 = 2.39 = 2.3.13