Tìm y nếu: 301 - (673,1: y + 47) = 6,7 x 30
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\(a.216\times y+y=3689\)
\(y\times\left(216+1\right)=3689\)
\(y\times217=3689\)
\(y=3689:217\)
\(y=17\)
\(b.y\times47-37\times y=20210\)
\(y\times\left(47-37\right)=20210\)
\(y\times10=20210\)
\(y=20210:10\)
\(y=2021\)
a)
216 * y + y = 3689
y * (216+1)=3689
y*217=3689
y=3689:217
y=17
b)
y * 47 - 37 * y = 20210
*y (47-37)=20210
y * 10 = 20210
y = 20210 :10
y= 2021
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a. y x 47 = 24064
y = 24064 : 47
y = 512
b. Y x 2 7 = 3 4 x 4 15 Y x 2 7 = 1 5 Y = 1 5 : 2 7 Y = 1 5 x 7 2 Y = 7 10
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B1:
\(a.301^2=\left(300+1\right)^2=300^2+2.300.1+1^2\\ =90000+600+1=90601\\ b.88^2+2.88.12+12^2=\left(88+12\right)^2=100^2=10000\\ c.99.100=100^2-100=10000-100=9900\\ d,153^2+94.153+47^2=153^2+2.153.47+47^2=\left(153+47\right)^2=200^2=40000\)
B2:
\(A=x^2-20x+101\\ =x^2-2.x.10+10^2+1\\ =\left(x-10\right)^2+1\ge1\forall x\in R\left(Vì:\left(x-10\right)^2\ge0\forall x\in R\right)\\ \Rightarrow min_A=1\Leftrightarrow x-10=0\Leftrightarrow x=10\)
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\(\dfrac{4}{51}\times y+y+y\times\dfrac{47}{51}=\dfrac{5}{4}+\dfrac{1}{6}\\y\times\left(\dfrac{4}{51}+1+\dfrac{47}{51}\right)= \dfrac{17}{12}\\ y\times2=\dfrac{17}{12}\\ y=\dfrac{17}{24}\)
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\(3x=4y=5z\)
\(\Rightarrow\frac{3x}{60}=\frac{4y}{60}=\frac{5z}{60}\Rightarrow\frac{x}{20}=\frac{y}{15}=\frac{z}{12}\)
Áp dụng tính chất dỹ tỉ số bằng nhau ta có:
\(\frac{x}{20}=\frac{y}{15}=\frac{z}{12}=\frac{x+y+z}{20+15+12}=\frac{47}{47}=1\)
\(\frac{x}{20}=1\Rightarrow x=20\)
\(\frac{y}{15}=1\Rightarrow y=15\)
\(\frac{z}{12}=1\Rightarrow z=12\)
Vậy\(x=20;y=15;z=12\)
Theo đề bài ,ta có:
\(3x=4y=5z\Leftrightarrow\frac{3x}{60}=\frac{4y}{60}=\frac{5z}{60}\)
\(\Leftrightarrow\frac{x}{20}=\frac{y}{15}=\frac{z}{12}=\frac{x+y+z}{20+15+12}=\frac{47}{47}=1\)
(Áp dụng tính chất dãy tỉ số bằng nhau)
Vậy \(\hept{\begin{cases}\frac{x}{20}=1\\\frac{y}{15}=1\\\frac{z}{12}=1\end{cases}\Leftrightarrow\hept{\begin{cases}x=20\\y=15\\z=12\end{cases}}}\)