ko dc viết mỗi kq
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Lời giải:
a.
$\frac{x}{-2}=\frac{-8}{x}$
$\Rightarrow x^2=(-2)(-8)=16=4^2=(-4)^2$
$\Rightarrow x=4$ hoặc $x=-4$
b.
$\frac{-5}{-14}=\frac{20}{6-5x}$
$\frac{5}{14}=\frac{20}{6-5x}$
$\Rightarrow 6-5x=20.14:5=56$
$x=-10$
e: \(=\dfrac{-5}{4}:\dfrac{-5}{8}+\dfrac{3}{2}\cdot\dfrac{-1}{2}=\dfrac{5}{4}\cdot\dfrac{8}{5}-\dfrac{3}{4}=2-\dfrac{3}{4}=\dfrac{5}{4}\)
f: \(=\dfrac{15}{7}\cdot\left(-7\right)\cdot\dfrac{-1}{10}=15\cdot\dfrac{1}{10}=\dfrac{3}{2}\)
g: \(=\dfrac{7}{10}\cdot\dfrac{-8}{7}:\dfrac{8}{15}-\dfrac{1}{3}\cdot\dfrac{1}{4}=\dfrac{-4}{5}\cdot\dfrac{15}{8}-\dfrac{1}{12}=\dfrac{-3}{2}-\dfrac{1}{12}=\dfrac{-19}{12}\)
\(d,\left(1-\dfrac{4}{7}\right)\left(\dfrac{-3}{8}-\dfrac{-5}{7}\right)=\dfrac{3}{7}.\dfrac{19}{56}=\dfrac{57}{392}\\ e,\left(-\dfrac{5}{6}\right)^2=\dfrac{25}{36}\\ c,\dfrac{4}{3}-\dfrac{1}{3}:5+\dfrac{3}{4}=\dfrac{4}{3}-\dfrac{1}{15}+\dfrac{3}{4}=\dfrac{19}{15}+\dfrac{3}{4}=\dfrac{121}{60}\)
a: \(=\dfrac{3}{11}+\dfrac{18}{66}=\dfrac{18}{66}+\dfrac{18}{66}=\dfrac{36}{66}=\dfrac{6}{11}\)
b: \(=\dfrac{2}{9}-\dfrac{5}{12}+\dfrac{3}{4}\)
\(=\dfrac{8}{36}-\dfrac{15}{36}+\dfrac{27}{36}=\dfrac{20}{36}=\dfrac{5}{9}\)
c: \(=\dfrac{3\cdot7-5}{35}\cdot\dfrac{-40-30}{16}\)
\(=\dfrac{16}{35}\cdot\dfrac{-70}{16}=-2\)
d: \(=\dfrac{1}{5}\cdot\dfrac{2-7}{4}-\dfrac{3}{4}\cdot\dfrac{4-11}{12}\)
\(=\dfrac{1}{5}\cdot\dfrac{-5}{4}-\dfrac{3}{4}\cdot\dfrac{-7}{12}\)
\(=\dfrac{-1}{4}+\dfrac{21}{48}=\dfrac{-12+21}{48}=\dfrac{9}{48}=\dfrac{3}{16}\)
a: \(\Leftrightarrow x^2=16\)
hay \(x\in\left\{4;-4\right\}\)
b: \(\Leftrightarrow\dfrac{20}{6-5x}=\dfrac{5}{14}\)
=>6-5x=56
=>5x=-50
hay x=-10
c: =>7/17=x/119=-35/y
=>x=49; y=-85
d: =>x/27=1/9+1/9=2/9
hay x=6
\(a,\dfrac{x}{-2}=\dfrac{-8}{x}\)
\(\Leftrightarrow x^2=16\Rightarrow\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)
\(b,\dfrac{5}{14}=\dfrac{20}{6-5x}\)
\(\Leftrightarrow30-25x=280\)
\(\Leftrightarrow25x=30-280=-250\)
\(\Leftrightarrow x=-10\)
\(c,\dfrac{7}{17}=\dfrac{x}{119}=\dfrac{-35}{y}\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{119.7}{17}=49\\y=\dfrac{-35.17}{7}=-85\end{matrix}\right.\)
\(d,\dfrac{x}{27}+\dfrac{-3}{27}=\dfrac{1}{9}\)
\(\dfrac{x-3}{27}=\dfrac{1}{9}\)
\(9x-27=27\)
\(9x=54\Rightarrow x=6\)
+ Quy ước: A: không sừng, a: có sừng
+ Bò không sừng có KG là: AA hoặc Aa
+ Bò có sừng có KG là: aa
a. Ptc: bò đực có sừng x bò cái ko sừng
aa x AA
F1: 100% Aa: ko sừng
b. F1 x F1: Aa x Aa
F2: 1AA : 2Aa : 1aa
KH: 3 ko sừng : 1 có sừng
c. Bò ko sừng F2 có KG là: AA hoặc Aa
Bò cái F1 có KG là Aa
+ P1: AA x Aa \(\rightarrow\) 1AA : 1Aa (100% bò ko sừng)
+ P2: Aa x Aa \(\rightarrow\) 1AA : 2Aa : 1aa (3 ko sừng : 1 có sừng)
\(a,\dfrac{8}{35}\)
\(b,\dfrac{15}{8}\)
\(c,\dfrac{30}{21}\)
\(d,\dfrac{72}{175}\)
const fi='inp.inp';
fo='out.inp';
var f1,f2:text;
st:array[1..100]of string;
i,n:integer;
begin
assign(f1,fi); reset(f1);
assign(f2,fo); rewrite(f2);
n:=0;
while not eof(f1) do
begin
n:=n+1;
readln(f1,st[n]);
end;
for i:=1 to n do
writeln(f2,length(st[i]));
close(f1);
close(f2);
end.
ko dc viết mỗi kq 
ko đc viết mỗi kq
ko đc viết mỗi kq =))
ko đc viết mỗi kq
c: 7/17=x/119=-35/y
\(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{119\cdot7}{17}=49\\y=\dfrac{-35\cdot17}{7}=-85\end{matrix}\right.\)
d: =>x/27-1/9=1/9
=>x/27=2/9
=>x=6