Question

GIÚP E!

Tìm x:

a) 7^5x : 49 = 7^28

b)5^2x . 5^14 = 5^30

 

Answer 1

Lời giải:

$7^{5x}:49=7^{28}$

$7^{5x}:7^2=7^{28}$

$7^{5x-2}=7^{28}$

$\Rightarrow 5x-2=28$

$\Rightarrow 5x=30$
$\Rightarrow x=6$

b.
$5^{2x}.5^{14}=5^{30}$

$5^{2x+14}=5^{30}$

$\Rightarrow 2x+14=30$

$\Rightarrow 2x=16$

$\Rightarrow x=8$

Answer 2

a) 7^5x:49=7^28

    7^5x:7^2=7^28

     7^5x=7^28.7^2

      7^5x=7^30

suy ra 5x=30

             x= 6

Answer 3

b) 5 mũ 2x. 5 mũ 14 =5 mũ 30

5^2x=5^16

suy ra 2x=16

x =16/2

x=8