Xx2,7+3,2xX+Xx1+Xx3,1=3200

Xx(2,7+3,2+1+3,1)=3200

Xx10=3200

X=3200:10

X=320

a)(x+1)+(x+2)+...+(x+30)=795

(x+x+...+x)+(1+2+3+...+30)=795

30x+465=795

30x=795-465

30x=330

x=330/30

x=11

b)(x+1)+(x+3)+...+(x+99)=5100

(x+x+...+x)+(1+3+...+99)=5100

50x+2500=5100

50x=5100-2500

50x=2600

x=2600/50

x=52

(4x+3) chia hết cho ( x-2 )=>x=-0,75

Trần Nguyễn Quốc Anh này cậu viết mõi đáp án thì ai mà chả lm đc . Tớ cần cả bài giai

4x+3 chia hết cho x-2

4x-8+8+3

4(x-2)+11

=>x-2 thuộc Ư(11)

Ư(11)={1;-1;11;-11}

x-2=1 =>x=3

x-2=-1 =>x=1

x-2=11 =>x=13

x-2=-11 =>x=-9

Vậy x thuộc {3;1;13;-9}

a: \(x\cdot12=621:5\)

=>\(x\cdot12=124,2\)

=>\(x=\dfrac{124.2}{12}=10.35\)

b: \(2.7\cdot x< 5\)

=>\(x< \dfrac{5}{2,7}\)

=>\(x< \dfrac{50}{27}\)

Bài 2:

a,\(|x-2|-3=-7\)

\(\Rightarrow|x-2|=-4\)

\(\Rightarrow x\in\varnothing\)

b,\(|x-5|+3=8\)

\(\Rightarrow|x-5|=5\)

\(\Rightarrow\left[{}\begin{matrix}x-5=5\\x-5=-5\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=10\\x=0\end{matrix}\right.\)

c,\(|x+3|-2+2x=5\)

\(\Rightarrow|x+3|+2x=7\)

\(\Rightarrow\left[{}\begin{matrix}x+3=2x=7,x+3\ge0\\-\left(x+3\right)+2x=7,x+3< 0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\frac{4}{3}\\x=10,x< -3\end{matrix}\right.,x\ge-3\)

\(\Rightarrow\left[{}\begin{matrix}x=\frac{4}{3}\\x\in\varnothing\end{matrix}\right.\)

d,\(|x-3,1|+|y-1,2|=0\)

Thay y =0

\(\Rightarrow|x-3,1|+|0-1,2|=0\)

\(\Rightarrow|x-3,1|+|-1,2|=0\)

\(\Rightarrow|x-3,1|+1,2=0\)

\(\Rightarrow|x-3,1|=-1,2\)

\(\Rightarrow x\in\varnothing\)

Bài 3:

a,(-2,7)+9-3,5)-1,2(-2)

=>-2,7-3,5+2,4

=>-3,8

b, (-2,3)(-0,4)-(-3,1)(-2,1)-13,2

=>0,92+3,1(-2,1)-13,2

=>0,92-6,51-13,2

=-18,79

Bài 3 : Tính :

a) \(\left(-2,7\right)+\left(-3,5\right)-1,2.\left(-2\right)\)

\(=\left(-6,2\right)-\left(-2,4\right)\)

\(=\left(-6,2\right)+2,4=-3,8\)

b) \(\left(-2,3\right).\left(-0,4\right)-\left(-3,1\right).\left(-2,1\right)-13,2\)

\(=0,92-6,51-13,2\)

\(=-18,79\)

\(3^{x+1}-2.3^x=243\\ \Rightarrow3^x.3-2.3^x=243\\ \Rightarrow3^x=3^5\\ \Rightarrow x=5\)

\(d.3^{x+1}-2.3^x=243\)

= 4906

bn k luon nha

1x2x3x4x5x6x7+10-12x12=4906

= 5194

(x+1)+(x+2)+(x+3)+......+(x+100)=5750=(x+x+x)+(1+2+3+.....+100)=5750   =100x+(1+100)×100:2=5750     =100x+101×50=5750                               =100x+5050=5750      =100x=5750-5050      =100x=700     x=700:100           x=7