- (x-1/2)2+1=71/4
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\(\dfrac{1}{12}\times\dfrac{4}{5}=\dfrac{4}{60}=\dfrac{1}{15}\\ \dfrac{9}{5}:\dfrac{4}{7}=\dfrac{9}{5}\times\dfrac{7}{4}=\dfrac{63}{20}\\ 4\times\dfrac{3}{7}=\dfrac{4\times3}{7}=\dfrac{12}{7}\\ \dfrac{1}{2}:5=\dfrac{1}{2}\times\dfrac{1}{5}=\dfrac{1}{10}\)
=>6x + 1 + 2 + 3 + 4 + 5 + 6 + = 71
=>6x + 21 = 71
6x = 71 - 21 = 50
=>x = 50/6 = 25/3
(x+1)+(x+2)+(x+3)+(x+4)+(x+6)=71
=x*5+1+2+3+4+5+6=71
=x*5+21=71
=x*5=71-21
=x*5=50
=x=50:5
x=10
vậy x=10
x+(x+1)+(x+2)+...+70+71=71
x+(x+1)+(x+2)+...+70=71-71
x+(x+1)+(x+2)+...+70=0
(x+70)+(x+1+69)+...=0
x+70=0
x=0-70
x=-70
k mk nhé thanks bạn
a) \(3x4^{x+1}-5.4^x=448\)
\(\Leftrightarrow4^x\left(3x4-5\right)=448\)
\(\Leftrightarrow4^x.7=448\)
\(\Leftrightarrow4^x=64=4^3\)
\(\Leftrightarrow x=3\)
b) \(5.\left(x-2\right)^3=4^3+71\left(x>1\right)\)
\(\Leftrightarrow5.\left(x-2\right)^3=64+71\)
\(\Leftrightarrow5.\left(x-2\right)^3=135\)
\(\Leftrightarrow\left(x-2\right)^3=27=3^3\)
\(\Leftrightarrow x-2=3\)
\(\Leftrightarrow x=5\)
9x - 1 = 9
=> 9x - 1 = 91
=> x - 1 = 1 => x = 2
2x . 25 = 64
2x . 25 = 27
=> x + 5 = 7
=> x = 2
\(a)\)
\(x+\left(x+1\right)+\left(x+2\right)+...+70+71=71\)
\(\Rightarrow x+\left(x+1\right)+\left(x+2\right)+...+70=0\)
Gọi số số hạng trong dãy số đó là \(a\)\(\left(a\ne0\right)\)
\(x+\left(x+1\right)+\left(x+2\right)+...+70\)
\(\Rightarrow\frac{\left(x+70\right).a}{2}\)
\(\Rightarrow\frac{\left(x+70\right).a}{2}=0\)
\(\Rightarrow\left(x+70\right).a=0\)
\(\Rightarrow x+70=0\)
\(\Rightarrow x=\left(-70\right)\)
\(b)\)
\(85+84+83+...+\left(x+2\right)+\left(x+1\right)+x=85\)
\(\Rightarrow84+83+...+\left(x+2\right)+\left(x+1\right)+x=0\)
Gọi số số hạng trong dãy tính là \(a\)\(\left(a\ne0\right)\)
\(84+83+...+\left(x+2\right)+\left(x+1\right)+x\)
\(\Rightarrow\frac{\left(x+84\right).a}{2}\)
\(\Rightarrow\frac{\left(x+84\right).a}{2}=0\)
\(\Rightarrow\left(x+84\right).a=0\)
\(\Rightarrow x+84=0\)
\(\Rightarrow x=\left(-84\right)\)
x+(x+1)+...+70+71=71
=>x+(x+1)+(x+2)+...+70=0
=(x+70)+(x+1+69)+...=0
=> x+70=0
x+-70