A) A= - ( 5 - 6 ) - ( 3-4+5-7)
B) P = ( 1+3+5+...+47+49)-(2+4+6+...+48+50)
Tính:
B=550 - 549 + 548 - 547 +... + 52 - 5 + 1.
1/1*2*3*4+1/2*3*4*5+1/3*4*5*6+...+1/47*48*49*
50
tổng của 1-2+3-4+5-6+...+47-48+49-50
50 + 48 + 46 + ... + 4 + 2 – 1 – 3 – 5 – ... – 47 – 49
Tính S/P biết:
S = 1/2 + 1/3 + 1/4 + 1/5 + ... + 1/49 + 1/50
P = 1/49 + 2/48 + 3/47 + ... + 48/2 +49/1
1+3+5+7+...+47+49+...+(-2)+(-4)+9(-6)+...+(-48)+(-50)
a) 99-97+95-93+91-89+ ..... +7-5+3-1
b) 50-49+48-47+46-45+.....+4-3+2-1
99-97+95-93+91-89+...+7-5+3-1 = ?
50-49+48-47+46-45+...+4-6+2-1 = ?