A = 258² - 242²/254² - 246²

A = (258 - 242).(258 + 242)/(254 - 246).(254 + 246)

A = 16.500/8.500

A = 2

=2 nha 

mình nhanh nhất

\(M=\frac{258^2-242^2}{254^2-246^2}\)

\(=\frac{\left(258-242\right)\left(258+242\right)}{\left(254-246\right)\left(254+246\right)}\)

\(=\frac{16.500}{8.500}\)

\(=2\)

p/s: chúc bạn hk tốt

\(M=\frac{258^2-242^2}{254^2-246^2}\)

\(M=\frac{\left(258-242\right)\left(258+242\right)}{\left(254-246\right)\left(254+246\right)}\)

\(M=\frac{16.500}{8.500}=\frac{16}{8}=2\)

a: \(A=\dfrac{\left(258-242\right)\left(258+242\right)}{\left(254-246\right)\left(254+246\right)}=\dfrac{16}{8}=2\)

b: \(=\left(263+37\right)^2=300^2=90000\)

c: \(=\left(136-46\right)^2=90^2=8100\)

d: \(=50^2-49^2+48^2-47^2+...+2^2-1^2\)

=50+49+...+2+1

=51x50:2=1275

\(\frac{258^2-242^2}{254^2-246^2}=\frac{\left(258+242\right)\left(258-242\right)}{\left(254+246\right)\left(254-246\right)}=\frac{500.16}{500.8}=2\)

\(263^2+74.263+37^2=263^2+2.37.263+37^2=\left(263+37\right)^2=300^2=90000\)

\(136^2-92.136+46^2=136^2-46.2.136+46^2=\left(136-46\right)^2=90^2=8100\)

\(=\left(50^2-49^2\right)+\left(48^2-47^2\right)+.....+\left(2^2-1^2\right)=\left(50+49\right)\left(50-49\right)+\left(48+47\right)\left(48-47\right)+....+\left(2+1\right)\left(2-1\right)=\left(50+49+....+1\right)=\frac{51.50}{2}=51.25=1275\)

Tính giá trị biểu thức sau:

a, A= \(258^2-\dfrac{242^2}{254^2}-246^2\approx\) 6047,1

b, B= \(263^2+74.263+37^2=90000\)

c, C= \(136^2-92.136+46^2=8100\)

d, D = \(\left(50^2+48^2+46^2+...+2^2\right)-\left(49^2+47^2+45^2+...+1^2\right)\)

= 22100 - 20825= 1275

\(\frac{63^2-47^2}{215^2-105^2}=\)  \(\frac{\left(63-47\right)\left(63+47\right)}{\left(215-105\right)\left(215+105\right)}\)

                           \(=\frac{16.110}{110.320}=\frac{16}{320}\)\(=\frac{1}{20}\)

các câu kia làm tương tự nha

Thanks bạn nhiều nhiều nha!

nhưng câu d với câu e mk khô hiểu lắm!

b: Sửa đề: \(B=263^2+54\cdot263+27^2\)

\(=263^2+2\cdot263\cdot27+27^2\)

\(=\left(263+27\right)^2=290^2=84100\)

c: \(C=136^2-2\cdot46\cdot136+46^2\)

\(=\left(136-46\right)^2=90^2=8100\)

d: \(D=\left(50^2-49^2\right)+\left(48^2-47^2\right)+...+\left(2^2-1^2\right)\)

\(=50+49+...+2+1\)

Số số hạng là (50-1):1+1=50(số)

Tổng là;

\(D=\dfrac{\left(50+1\right)\cdot50}{2}=51\cdot25=1225\)