a+b+c=? biet a=5, b=4 ,c=6
tim 3 so a,b,c biet a+b+c=100 va a:4=b:6=c:5
Áp dụng tính chất của dãy các tỉ số bằng nhau, ta có:
\(\frac{a}{4}=\frac{b}{6}=\frac{c}{5}=\frac{a+b+c}{4+5+6}=\frac{100}{15}=\frac{20}{3}\)
\(\Rightarrow a=\frac{20}{3}.4=\frac{80}{3}\)
\(b=\frac{20}{3}.6=40\)
\(c=\frac{20}{3}.5=\frac{100}{3}\)
\(a:4=b:5=c:6\)
\(\Rightarrow\frac{a}{4}=\frac{b}{5}=\frac{c}{6}=\frac{a+b+c}{4+5+6}=\frac{100}{15}=\frac{20}{3}\)
\(\Leftrightarrow\frac{a}{4}=\frac{20}{3}\)\(\Rightarrow a=\frac{4.20}{3}=\frac{80}{3}\)
\(\Leftrightarrow\frac{b}{5}=\frac{20}{3}\Rightarrow b=\frac{5.20}{3}=\frac{100}{3}\)
\(\Leftrightarrow\frac{c}{6}=\frac{20}{3}\Rightarrow c=\frac{6.20}{3}=40\)
Vậy \(a=\frac{80}{3};b=\frac{100}{3};c=40\)
tim a,b,c,d biet rang a:b:c:d= 7:6:5:4 va a+b+c+d =66
Tim cac so a,b,c,d biet a:b:c:d=7:6:5:4 va a+b+c+d=66
Taa co : a:b:c:d=7:6:5:4 va a+b+c+d=66
\(a:b:c:d=7:6:5:4=\frac{a}{7}=\frac{b}{6}=\frac{c}{5}=\frac{d}{4}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{a}{7}=\frac{b}{6}=\frac{c}{5}=\frac{d}{4}=\frac{a+b+c+d}{7+6+5+4}=\frac{66}{22}=3\)
Suy ra : \(\frac{a}{7}=3\Rightarrow a=3.7=21\)
\(\frac{b}{6}=3\Rightarrow b=3.6=18\)
\(\frac{c}{5}=3\Rightarrow c=3.5=15\)
\(\frac{d}{4}=3\Rightarrow d=3.4=12\)
TÌM a,b,c BIET
a,\(a+b=-9,b+c=2,c+a=-3\)
b,\(a+b=\dfrac{1}{2},b+c=\dfrac{3}{4},c+a=-\dfrac{5}{6}\)
c,\(a+b=2,b+c=6,c+a=3\)
d,\(a+b=\dfrac{5}{6},b+c=\dfrac{3}{4},c+a=\dfrac{5}{3}\)
a,
\(a+b=-9\\ b+c=2\\ c+a=-3\\ \Rightarrow a+b+b+c+c+a=\left(-9\right)+2+\left(-3\right)\\ 2a+2b+2c=-10\\ 2\left(a+b+c\right)=-10\\ a+b+c=-5\\ a+b=-9\\ \Rightarrow a+b+c=-5\Leftrightarrow\left(-9\right)+c=-5\Rightarrow c=4\\ b+c=2\\ \Rightarrow a+b+c=-5\Leftrightarrow a+2=-5\Rightarrow a=-7\\ c+a=-3\\ \Rightarrow a+b+c=-5\Leftrightarrow\left(-3\right)+b=-5\Rightarrow b=-2\)
Vậy \(a=-7;b=-2;c=5\)
b,
\(a+b=\dfrac{1}{2}\\ b+c=\dfrac{3}{4}\\ c+a=\dfrac{-5}{6}\\ \Rightarrow a+b+b+c+c+a=\dfrac{1}{2}+\dfrac{3}{4}+\dfrac{-5}{6}\\ 2a+2b+2c=\dfrac{6}{12}+\dfrac{9}{12}+\dfrac{-10}{12}\\ 2\left(a+b+c\right)=\dfrac{5}{12}\\ a+b+c=\dfrac{5}{24}\\ a+b=\dfrac{1}{2}\\ \Rightarrow a+b+c=\dfrac{5}{24}\Leftrightarrow\dfrac{1}{2}+c=\dfrac{5}{24}\Rightarrow c=\dfrac{-7}{24}\\ b+c=\dfrac{3}{4}\\ \Rightarrow a+b+c=\dfrac{5}{24}\Leftrightarrow a+\dfrac{3}{4}=\dfrac{5}{24}\Rightarrow a=\dfrac{-13}{24}\\ a+c=\dfrac{-5}{6}\\ \Rightarrow a+b+c=\dfrac{5}{24}\Leftrightarrow b+\dfrac{-5}{6}=\dfrac{5}{24}\Rightarrow b=\dfrac{25}{24}\)
Vậy \(a=\dfrac{-13}{24};b=\dfrac{25}{24};c=\dfrac{-7}{24}\)
c,
\(a+b=2\\ b+c=6\\ c+a=3\\ \Rightarrow a+b+b+c+c+a=2+6+3\\ 2a+2b+2c=11\\ 2\left(a+b+c\right)=11\\ a+b+c=5,5\\ a+b=2\\ \Rightarrow a+b+c=5,5\Leftrightarrow2+c=5,5\Rightarrow c=3,5\\ b+c=6\\ \Rightarrow a+b+c=5,5\Leftrightarrow a+6=5,5\Rightarrow a=-0,5\\ c+a=3\\ \Rightarrow a+b+c=5,5\Leftrightarrow b+3=5,5\Rightarrow b=2,5\)
Vậy \(a=-0,5;b=2,5;c=3,5\)
d,
\(a+b=\dfrac{5}{6}\\ b+c=\dfrac{3}{4}\\ c+a=\dfrac{5}{3}\\ \Rightarrow a+b+b+c+c+a=\dfrac{5}{6}+\dfrac{3}{4}+\dfrac{5}{3}\\ 2a+2b+2c=\dfrac{10}{12}+\dfrac{9}{12}+\dfrac{20}{12}\\ 2\left(a+b+c\right)=\dfrac{13}{4}\\ a+b+c=\dfrac{13}{8}\\ a+b=\dfrac{5}{6}\\ \Rightarrow a+b+c=\dfrac{13}{8}\Leftrightarrow\dfrac{5}{6}+c=\dfrac{13}{8}\Rightarrow c=\dfrac{19}{24}\\ b+c=\dfrac{3}{4}\\ \Rightarrow a+b+c=\dfrac{13}{8}\Leftrightarrow a+\dfrac{3}{4}=\dfrac{13}{8}\Rightarrow a=\dfrac{7}{8}\\ c+a=\dfrac{5}{3}\\ \Rightarrow a+b+c=\dfrac{13}{8}\Leftrightarrow b+\dfrac{5}{3}=\dfrac{13}{8}\Rightarrow b=\dfrac{-1}{24}\)
Vậy \(a=\dfrac{7}{8};b=\dfrac{-1}{24};c=\dfrac{19}{24}\)
\(\left\{{}\begin{matrix}a+b=-9\\b+c=2\\c+a=-3\end{matrix}\right.\)
\(\Rightarrow a+b+b+c+c+a=\left(-9\right)+2+\left(-3\right)\)
\(\Rightarrow2a+2b+2c=-10\)
\(\Rightarrow2\left(a+b+c\right)=-10\)
\(\Rightarrow a+b+c=-5\)
\(\Rightarrow\left\{{}\begin{matrix}c=-5-9=-14\\a=-5-2=-7\\b=-5-\left(-3\right)=-2\end{matrix}\right.\)
Tim a,b,c biet 5a - 3b -4c=46 va a-1/2=b+3/4=c-5/6
https://qanda.ai/vi/solutions/3C1BcC2xFx
1) Cho diem A ( 1; -5 ). Tim toa do B biet A la anh cua B qua phep tinh tien theo vecto v = (2;1)
A. (6;-1) B. (1;-6) C(-3;-4) D. (3;4)
a,tim a biet da thuc A(x)=ax2- 1/2x +1 co 1 nghiem la -1/2
b, tim a,b cua da thuc :B(x)= ax2+bx+5 biet B(1)=6 va B(-2) = 15
c, cho da thuc C(x)= ax+b .Tim a,b biet :
x=4 la nhgiem cua C(x)va C(2)=1
tim a,b,c biet:
14,abc=2,14+12/8+1,25+13/5+6/4
Cho cac so nguyen duong a,b,c,x,y,z
1, Biet 1/a = 3/b + c = 5/c + a. Hay rut gon phan so A = a/2b - c
2. Biet a/b = 2b/cc = 4c/a. Hay rut gon phan so B = ab + bc + ca/a2 + b + c2
3. Biet x/a = y/b =z/c. Hay rut gon phan so C = x*y*z*(b+c)*(c+a)*(a+b)/a*b*c(y+z)*(z+x)*(x+y)
4. Biet ab/a + 2b = 2/5; bc/b + 2c = 3/4; ca/c +2a = 3/5. Hay rut gon phan so D = abc/ab+bc+ca
5. Biet 3/a -4b = 5c. Hay rut gon phan so E = 3bc + ab - 4ac/6bc - 8ac -ab
Giup minh nhe! Ai lam duoc va dung cho tick.
Thanks cac ban
xin lỗi tớ ấn nhầm chỗ M=7 tớ làm lại rồi đó
ban tra loi het cac cau hoi phia tren kia ho minh dc ko?