P=\(\left(\frac{\sqrt{x}}{\sqrt{x}-2}+\frac{\sqrt{x}}{\sqrt{x}+2}\right)\cdot\frac{x-4}{\sqrt{4x}}\)

a/rút gon P

b/Tìm x để P >3

Ta có : abc - cba = ( 100a + 10b + c ) - ( 100c + 10b + a )

                              = 100a + 10b + c - 100c - 10b - a

                              = ( 100a - a ) + ( 10b - 10b ) + ( c -100c )

                              = 99a + ( -99c )

                              = 99 (a - c )

Vì 99 chia hết cho 99 nên 99( a - c ) chia hết cho 99 => abc - cba  chia hết cho 99 ( đpcm )

a)\(\dfrac{2}{\sqrt{7}-5}\)-\(\dfrac{2}{\sqrt{7}+5}\)

b)\(\dfrac{\sqrt{7}+5}{\sqrt{7}-5}\)+\(\dfrac{\sqrt{7}-5}{\sqrt{7}+5}\)

chung to gia tri cac bieu thuc sau la so huu ti

dat vao hai dau day dan 1 hieu dien the 600mV biet cuong do dong dien chay qua day 10mA

a)thiet ke so do mach dien.

b)tinh dien tro cua day

c)tang hieu dien the len 10 lan giu nguyen gia tri dien tro thi luc do se ra sao

d) giu nguyen hieu dien the thay bang 1 day dan khac co dien tro tang them 3Ω thi luc do dong dien nhu the nao