Đáp án:
x-$\frac{x+1}{3}$=$\frac{2x+1}{5}$
<=>$\frac{15x}{15}$-$\frac{5(x+1)}{15}$=$\frac{3(2x+1}{15}$
=>15x-5(x+1)=3(2x+1)
<=>15x-5x-5=6x+3
<=>10x-5=6x+3
<=>10x-6x=3+5
<=>4x=2
<=>x=2
b)$\frac{2x-1}{3}$-$\frac{5x+2}{7}$ =x+13
<=>$\frac{7(2x-1)}{21}$-$\frac{3(5x+2)}{21}$ =x+13
<=>$\frac{7(2x-1)}{21}$-$\frac{3(5x+2)}{21}$ =$\frac{21(x+13)}{21}$
=>14x-7-15x-6=21(x+13)
<=>-x-13=21(x+13)
<=>$\frac{-x-13}{21}$=x+13
<=>$\frac{-22x}{21}$-$\frac{286}{13}$=0
<=>-$\frac{22(x+13)}{21}$=0
* x+13=0
<=>x=-13
c)(x-1)²+(x+3)²=2(x-2).(x+1)+38
<=>x²-2x+1+x²+6x+3²=(2x-4).(x+1)+38
<=>2x²+4x+10=2x²+2x-4x-4+38
<=>2x²+4x+10-2x²-2x+4x=-4+38
<=>6x=34-10
<=>x=4
cho mik 5 sao + câu trả lời hay nhất+ cảm ơn nha
