a x ( 1 + 2 + 3 + ..+50) = 127500
a x [ ( 50 + 1 ) x 50 : 2 ]= 127500
a x 1275 = 127500
a = 127500 : 1275
a = 100
a+a x 2+a x 3+....+a x 50=12750
=>a x (1+2+3+...+50)=12750
tổng trong ngoặc là:\(1+2+3+...+50=\frac{50x\left(50+1\right)}{2}=1275\)
=>a x 1275=12750
=>a=10
vậy a=10
a+ax2+ax3+...+ax50=127500
=>ax(1+2+3+...+50)=127500
=>ax1275=127500
=>a=100
=a*1+a*2+a*3+...+a*50=127500
=(1+2+2+...+50)*50a=127500
=1275*50a=127500
=127500/1275=50a
=100=50a
a=100/50=2
Vậy a = 2
nhớ k cho mik nhá ^^
