a) (2x - 7) + 16= -21
=> 2x - 7 = -21 - 16 = (-21) + (-16)
=> 2x - 7 = -37
=> 2x = -37 + 7 = -30
=> x = -30 : 2 = -15
b) 72 - 3 (5 - x) = 108
=> 3. (5 - x) = 72 - 108 = -36
=> 5 - x = -36 : 3 = -12
=> x = 5 - (-12) = 5 + 12
=> x = 17
d) (x + 1) + (x + 2) + (x + 3) +.....+ (x + 50) = 1625
=> x + 1 + x + 2 + x + 3 +....+x + 50 = 1625
=> (x + x + x + .... + x) + (1 + 2 + 3 + .... + 50) = 1625
Từ 1 → 50 có: (50 - 1) + 1 = 50 (số hạng)
=> Có 50 x
Ta có: (x + x + x + .... + x) + (1 + 2 + 3 + .... + 50) = 1625
=> 50. x + (1 + 2 + 3 + .... + 50) = 1625
Tổng các số từ 1 → 50: (50 + 1). 50 = 2550
=> 50. x + 2550 = 1625
=> 50. x = 1625 - 2550 = -925
=> x = (-925) : 50 = \(-\frac{37}{2}\)
P/s: Ko chắc!
\(\text{a) }\left(2x-7\right)+16=-21\)
\(\Leftrightarrow2x-7+16=-21\)
\(\Leftrightarrow2x=-30\)
\(\Rightarrow x=-15\)
\(\text{b) }72-3\left(5-x\right)=108\)
\(\Leftrightarrow3\left(5-x\right)=-36\)
\(\Leftrightarrow5-x=-12\)
\(\Rightarrow x=17\)
\(\text{d) }\left(x+1\right)+\left(x+2\right)+...+\left(x+50\right)=1625\)
\(\Leftrightarrow50x+1275=1625\)
\(\Rightarrow x=7\)
\(\text{c) }\left(x-11\right)^3+3^2.5=37\)
\(\Leftrightarrow\left(x-11\right)^3=-8\)
\(\Leftrightarrow x-11=-2\)
\(\Rightarrow x=9\)
