cụ thể nhat r ak :)))

cụ thể nhat r ak :)))

đk x ≠ 1; x ≠ -1

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

=> x =1(ko t/m) ; x=-1(ko t/m)

\(\dfrac{728}{725}=\dfrac{728.821}{595225}=\dfrac{597688}{595225};\dfrac{824}{821}=\dfrac{824.725}{821.725}=\dfrac{597400}{595225}\\ m\text{a}597688>597400=>\dfrac{728}{725}>\dfrac{824}{821}\)

ko bik bội chung cua 725 va 821 nên nhan hơi to :))

\(\text{a},x^2-4x+3x-12-x^2+16=0\\ -x+4=0\\ x=4\\ b,x^2-1-2x+2=0\\ x^2-2x+1=0\\ \left(x-1\right)^2=0\\ x-1=0\\ x=1\)

x ≥ 0

x ≥ -2/3

x ≤ 4/5

x > 2

 sai đề r

\(\text{a},\left(x+\dfrac{2}{3}\right)^3=\left(\dfrac{5}{4}\right)^3\\ x+\dfrac{2}{3}=\dfrac{5}{4}\\ x=\dfrac{5}{4}-\dfrac{2}{3}=\dfrac{5.3-3.4}{12}=\dfrac{7}{12}\\ b,\left(x-\dfrac{1}{2}\right)^3=\left(\dfrac{2}{7}\right)^3\\ x-\dfrac{1}{2}=\dfrac{2}{7}\\ x=\dfrac{2}{7}+\dfrac{1}{2}=\dfrac{2.2+1.7}{14}=\dfrac{11}{14}\)

a, Xét tam giac HD va tam giac BKC có

aD = BC ( abcd la hình thag can )

góc ahd = góc bkc = 90 độ

góc bck = góc adh (  abcd la hình thag can)

=> tam giac HD = tam giac BKC ( ch -gn)

=> HD = KC