Question

tìm a biết : a + a x 2 + a x 3 + .....+ a x 50 = 12750

Answer 1

a x ( 1 + 2 + 3 + ..+50) = 127500

a x [ ( 50 + 1 ) x 50 : 2 ]= 127500

a x  1275 = 127500

a = 127500 : 1275

a = 100

Answer 2

a = 10

Nhớ k cho mình nhé

Answer 3

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

Answer 4

a+ax2+ax3+...+ax50=127500

=>ax(1+2+3+...+50)=127500

=>ax1275=127500

=>a=100

Answer 5

=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 ^^