Question

Va rog ex 7 si 8 sau doar 7

Answer 1

8.

a)rad(x)=9=>x=81;

d)rad(x)+3=4
rad(x)=1=>x=1;

b)rad(3x)=21
3x=441
x=147;

e)rad(x)-5=2
rad(x)=7
x=49;

c)rad(2x-3)=5;
avem conditia:2x-3>0
2x>3
x>3/2;

deci: 2x-3=25
2x=28
x=14>3/2,deci x=14

f)rad(x+2)=3
conditie:x+2>0
x>-2

x+2=9
x=7>-2=>x=7;



7.

Alea mai grele..

c)



rad(1+4+4*5+4*5^2+4*5^3...+4*5^2011)=

rad(1+4(1+5+5^2+...+5^2011)=
rad(1+4[(5^2012-1)/5-1])=
rad(1+4*[(5^2012-1)/4])=rad(1+[(5^2012-1)/4])
=rad([(5^2012+3)/4])
=5^1006/2 +rad(2)/2


i)rad((1+2+3+...+72)/73)
=rad(36*73/73)
rad(36)=6

j)rad(25)-rad(1+2+3..+8)/3

=5-rad(36)/3
5-2
=3