Cho \(x=-98;a=61;m=-25\)
Tính giá trị các biểu thức sau :
a) \(x+8-x-22\)
b) \(-x-a+12+a\)
c) \(a-m+7-8+m\)
d) \(m-24-x+24+x\)
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Ta có\(M=\left[\left(1+\frac{1}{98}\right)+\left(\frac{1}{2}+\frac{1}{97}\right)+...+\left(\frac{1}{49}+\frac{1}{50}\right)\right].2.3...98\)
\(=\left[\frac{99}{1.98}+\frac{99}{2.97}+...+\frac{99}{49.50}\right].2.3...98=99\left(\frac{1}{1.98}+\frac{1}{2.97}+...+\frac{1}{49.50}\right).2.3...98\)
\(=99\left(\frac{k_1+k_2+...+k_{49}}{1.2.3...98}\right).2.3...98\left(k_1,k_2...k_{49}\varepsilonℕ^∗\right)=99\left(k_1+k_2+...+k_{49}\right)⋮99\Rightarrow M⋮99\left(đpcm\right)\)
98 x a + b x 98 - c x 98 = 98 x (a+b-c) = 98 x 160 = 15680
\(x\times98+x:0,5=2017\)
\(x\times98+x\times2=2017\)
\(x\times\left(98+2\right)=2017\)
\(x\times100=2017\)
\(x=2017:100\)
\(x=20,17\)
\(\frac{x-1}{99}+\frac{x-2}{98}+\frac{x-3}{97}+\frac{x-4}{96}=4\)
\(\Leftrightarrow\left(\frac{x-1}{99}+\left(-1\right)\right)+\left(\frac{x-2}{98}+\left(-1\right)\right)+\left(\frac{x-3}{97}+\left(-1\right)\right)+\left(\frac{x-4}{96}+\left(-1\right)\right)=0\)
\(\Leftrightarrow\frac{x-100}{99}+\frac{x-100}{98}+\frac{x-100}{97}+\frac{x-100}{96}=0\)
\(\Leftrightarrow\left(x-1\right).\left(\frac{1}{99}+\frac{1}{98}+\frac{1}{97}+\frac{1}{96}\right)=0\)
\(\Leftrightarrow x-1=0\)
\(\Leftrightarrow x=1\)
a) \(-98 + 8 -(-98) -22 = 8-22=-14\)
b) \(-(-98)-61+12+61=-(-98) + 12 = 110\)
c) \(61-(-25) +7-8+(-25)=61-1=60\)
d) \((-25)-24-(-98)+24+(-98)=-25\)
a) \(x+8+x-22\)
Tại X= -98
\(-98+8-\left(-98\right)-22=-98+8-98-22=8-22=-14\)
b) \(-x-a+12+a\)
\(\Leftrightarrow-\left(-98\right)-61+12+61=12+98=110\)
c) \(a-m+7-8+m\)
\(\Leftrightarrow61-\left(-25\right)+7-8+\left(-25\right)=61+25+7-8-25=61-1=60\)d) \(m-24-x+24+x\)
\(\Leftrightarrow-25-24-\left(-98\right)+24+\left(-98\right)=-25+98-98=-25\)