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ak nhầm

gọi số hs lớp 7a 

2x-5=(-17)+12

2x-5=-5

2x=-5+5

x=0:2

x=0

\(2x-5=(-17)+12\)

\(2x=(-17)+12+5\)

\(2x=0\)

\(x=0\)

Vậy \(x=0\)

\(2x-5=\left(-17\right)+12\)

\(2x-5=5\)

\(2x=10\)

\(x=5\)

\(5^{x+2}-5^x=3.10^3\)

\(\Rightarrow5^x\left(5^2-1\right)=3000\)

\(\Rightarrow5^x.24=3000\Rightarrow5^x=125=5^3\)

\(\Rightarrow x=3\)

\(5^{x+2}-5^x=3\cdot10^3\)

\(\Leftrightarrow5^x\cdot24=3000\)

\(\Leftrightarrow x=3\)

Khoảng cách : `2`

Số số hạng là : `(99-1):2+1=50`

Tổng là : `(99+1) xx 50 :2=2500`

1+3+5+7+....+99

Ta có: 3-1=2;5-3=2;7-5=2;... nên dãy số trên gồm các số hạng cách đều nhau 2 đơn vị.

Số số hạng của dãy số đó là:

(99-1):2+1= 50(số)

Tổng các số hạng của dãy số đó là:

(99+1) x 50:2=2500

                          Đáp số : 2500

Viết phép tính k hiểu

a: \(\left(\dfrac{3x-x^2}{9-x^2}-1\right):\left(\dfrac{9-x^2}{x^2+x-6}-\dfrac{x-3}{2-x}-\dfrac{x+2}{x+3}\right)\)

\(=\left(\dfrac{x}{x+3}-1\right):\dfrac{9-x^2+x^2-9-x^2+4}{\left(x-2\right)\left(x+3\right)}\)

\(=\dfrac{x-x-3}{x+3}\cdot\dfrac{\left(x+3\right)\left(x-2\right)}{-x^2+4}\)

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

b: \(\left(\dfrac{x+2}{x-1}-\dfrac{x-1}{x+2}+\dfrac{x+5}{x^2+x-2}\right)\cdot\left(x^3-1\right)\)

\(=\dfrac{x^2+4x+4-x^2+2x-1+x+5}{\left(x+2\right)\left(x-1\right)}\cdot\dfrac{\left(x-1\right)\left(x^2+x+1\right)}{1}\)

\(=\dfrac{7x+8}{\left(x+2\right)}\cdot\dfrac{x^2+x+1}{1}\)

=5^3+3^9

=125+19683

=19808

5 x 6 : 5 x 3 + 3 x 2 x 3 x 7 

= 30 : 15 + 126 

= 2 + 126 

= 128

5x6:5x3+3x2x3x7

=5x(6:3)+3x2x3x7

=5x2+126

=10+126

=136

|2x+3|=|x-3|

(2x+3)²=(x-3)²

4x²+12x+9=x²-6x+9

3x² + 18x = 0

x=0 hoặc x=-6

có 3 cách trọn chữ số hàng đơn vị

có 4 cách trọn chữ số hàng phần nghìn

có 4 cách trọn chữ số hàng phần trăm

có 3 cách trọn chữ số hàng phần mười

có số số là: 3x4x4x3= 144 số

đ/s:...

ko chắc chắn, đúng k mk nhé

đáp án là 24

các bạn giải lời giải ra hộ m nhé !

Bài giải

Có 3 cách chọn chữ số hàng đơn vị

Có 4 cách chọn chữ số hàng nghìn

Có 4 cách chọn chữ số hàng trăm

Có 3 cách chọn chữ số hàng chục

Có số số là :

 3 x 4 x 4 x 3 = 144 (số )

Đáp số : 144 số

\(\frac{38}{10}:2x=\frac{1}{4}\times\frac{3}{8}\)

\(\frac{38}{10}:2x=\frac{3}{32}\)

\(2x=\frac{38}{10}:\frac{3}{32}\)

\(2x=\frac{38}{10}\times\frac{32}{3}\)

\(2x=\frac{608}{15}\)

\(x=\frac{608}{15}\times\frac{1}{2}\)

\(x=\frac{304}{15}\)