Câu hỏi của Đỗ Khương Duy

Question

Tìm x biết: a. x $⋮$ 12; 25; 30 và 0$\le$ x$\le$ 500

b.(3x-2$^4$ )$\times$ 7$^3$ =2$\times$ 7$^4$

c. \x-5\=16+2$\times$ (-3)

Mashiro Shiina · Accepted Answer

$x⋮12;25;30\Rightarrow x\in BC\left(12;25;30\right)$

$12=2^2.3;25=5^2;30=2.3.5$

$BCNN\left(12;25;30\right)=2^2.3.5^2=300$

$BC\left(12;25;30\right)=B\left(300\right)$

$B\left(300\right)=\left\{0;300;600;....\right\}$

$0\le x\le500\Rightarrow x=300$

$\left(3x-2^4\right).7^3=2.7^4$

$\left(3x-16\right)=2.7$

$3x-16=14$

$3x=30$

$x=10$

$\left|x-5\right|=16+2.\left(-3\right)$

$\left|x-5\right|=10$

$\Leftrightarrow x-5=10\Rightarrow x=15$

$\Leftrightarrow x-5=-10\Rightarrow x=-5$Câu trả lời: $x⋮12;25;30\Rightarrow x\in BC\left(12;25;30\right)$