Question

Tìm x biết:

a) ( 19x + 2 . 5^2 ) : 14 = ( 13 - 8 )^2 - 4^2

b)2 . 3^x = 10 . 3^12 + 8 . 27^4

Answer 1

a) \(\left(19x+2\cdot5^2\right)\div14=\left(13-8\right)^2-4^2\)

\(\left(19x+2\cdot25\right)\div14=5^2-16\)

\(\left(19x+50\right)\div14=25-16=9\)

\(19x+50=9\cdot14=126\)

\(19x=126-50=76\)

\(x=76\div19=4\)

b) \(2\cdot3^x=10\cdot3^{12}+8\cdot\left(3^3\right)^4\)

\(2\cdot3^x=\left(10+8\right)\cdot3^{12}\)

\(2\cdot3^x=18\cdot3^{12}\)

\(\Rightarrow2\cdot3^x=2\cdot3^2\cdot3^{12}\Rightarrow2\cdot3^x=2\cdot3^{15}\Rightarrow x=15\)

Answer 2

a, \left(19.x+2.5^2\right)\div14=\left(13-8\right)^2-4^2(19.x+2.52)÷14=(13−8)2−42
\left(19.x+2.25\right)\div14=5^2-4^2(19.x+2.25)÷14=52−42
\left(19.x+2.25\right)\div14=25-16(19.x+2.25)÷14=25−16
\left(19.x+50\right)\div14=9(19.x+50)÷14=9
\left(19.x+50\right)=9.14(19.x+50)=9.14
19.x+50=12619.x+50=126
19.x=126-5019.x=126−50
19.x=7619.x=76
\Rightarrow x=76\div19⇒x=76÷19
\Rightarrow x=4⇒x=4
Vậy x = 4
b, 2.3^x=10.3^{12}+8.27^42.3x=10.312+8.274
2.3^x=10.3^{12}+8.\left(3^3\right)^42.3x=10.312+8.(33)4
2.3^x=10.3^{12}+8.3^{12}2.3x=10.312+8.312
2.3^x=\left(10+8\right).3^{12}2.3x=(10+8).312
2.3^x=18.3^{12}2.3x=18.312
2.3^x=2.3^3.3^{12}2.3x=2.33.312
2.3^x=2.3^{15}2.3x=2.315
\Rightarrow x=15⇒x=15
Vậy x = 15

Answer 3

a.(19x+2×25):14=5^2-16 (19x+50):14=25-16 (19x+50):14=9 (19x+50)=9×14=126 19x+50=126 19x=126-50=76 x=76:19 x=4 b.2×3^x=10×3^12+2^3×3^12 2×3^x=3^12×(10+8) 2×3^x=3^12×18 2×3^x=3^12×3^2×2 2×3^x=3^14×2 Suy ra:3^x=3^14 Hay x=14