Bài 2:

a: =>x:16=30,34+3,4-24,3=9,44

=>x=151,04

b: Đề thiếu rồi bạn

a)\(37.x6.5-7.5x3.4-6.6x7.5+3.5x37.5\)

=\(7.5x5x6.5-7.5x3.4-6.6x7.5+3.5x7.5x5\)

=\(7.5x\left(5x6.5-3.4-6.6+3.5x5\right)\)

=\(7.5x\left(2x6.5-10\right)\)

=\(7.5x\left(13-10\right)\)

=\(7.5x3\)

=\(22.5\)

Phần b phải là \(45^3\)chứ bạn

\(a,2,3:0,25+7,7.4\\ =2,3.4+7,7.4\\ =\left(2,3+7,7\right).4=10.4=40\\ b,4,2.8+5,8:0,125\\ =4,2.8+5,8.8\\ =\left(4,2+5,8\right).8=10.8=80\\ c,3,4.4+5,6:0,25+4\\ =3,4.4+5,6.4+4\\ =\left(3,4+5,6+1\right).4=10.4=40\\ d,4:0,2+12:0,5+1,2:0,25\\ =4.5+12.2+1,2.4\\ 4.5+6.4+1,2.4\\ =4\left(5+6+1,2\right)\\ =4.12,2=48,8\)

❤

a: \(\left(-2,5\cdot0,38\cdot0,4\right)-\left\lbrack0,125\cdot3,15\cdot\left(-8\right)\right\rbrack\)

\(=-1\cdot0,38+\left\lbrack0,125\cdot8\cdot3,15\right\rbrack\)

=3,15-0,38

=2,77

b: \(\left\lbrack\left(-20,83\right)\cdot0,2+\left(-9,17\right)\cdot0,2\right\rbrack:\left\lbrack2,47\cdot0,5-\left(-3,53\right)\cdot0,5\right\rbrack\)

\(=0,2\cdot\frac{\left(-20,83-9,17\right)}{0,5\cdot\left(2,47+3,53\right)}=0.2\cdot\frac{-30}{0,5\cdot6}=0,2\cdot\frac{-30}{3}=0,2\cdot\left(-10\right)\)

=-5

x kia là nhân hả bạn ? 

Bài 3: 

b: \(x^2+2x+1=\left(x+1\right)^2\)

c: \(x^2-16=\left(x-4\right)\left(x+4\right)\)

d: \(\left(2x-1\right)^2-\left(x+3\right)^2\)

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

\(=\left(x-4\right)\left(3x+2\right)\)

kc: 2,3-1,2=1,1

      ...............

so so hang : (99,100-1,2):1,1+1=90

tong day so: (99,100+1,2) x 90:2=4513,5

Đáp số:x=102

theo công thức:tổng=[số cuối+số đầu]:khoảng cách+1.

⇔3,4:1,7-0,2

⇔2-0,2

⇔1,8