Toán Lớp 7: a) 4^7×3^21/6^14×9^3
b) 2^7x/2^4x=64
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Toán Lớp 7: a) 4^7×3^21/6^14×9^3
b) 2^7x/2^4x=64
Comments ( 2 )
Giải đáp:
Lời giải và giải thích chi tiết:
$a)\dfrac{4^7.3^{21}}{6^{14}.9^3}$
=$\dfrac{(2^2)^7.3^{21}}{(2.3)^{14}.(3^2)^3}$
=$\dfrac{2^{14}.3^{21}}{2^{14}.3^{14}.3^{6}}$
=$\dfrac{2^{14}.3^{21}}{2^{14}.3^{20}}$
=$\dfrac{3^{21}}{3^{20}}$
=$3$
b)$2^{7x}$:$2^{4x}$=$64$
$2^{7x}$:$2^{4x}$=$2^6$
$3x=6$
$x=2$
Xin ctlhn
a, (4^7. 3^21)/(6^14. 9^3)
= ((2^2)^7. 3^21)/((2.3)^14. (3^2)^3)
= (2^14. 3^21)/(2^14. 3^14. 3^6)
= (2^14. 3^21)/(2^14. 3^20)
= (3^21)/(3^20)
= 3
b, (2^(7x))/(2^(4x)) = 64
=> 2^(7x) : 2^(4x) = 2^6
=> 2^(7x-4x) = 2^6
=> 7x – 4x = 6
=> 3x = 6
=> x = 6:3
=> x = 2
Vậy x = 2