\(a)y-6:2-\left(48-24x2:6-3\right)=0\)\(0\)

    \(y-3-\left(48-48:6-3\right)=0\)

    \(y-3-\left(48-8-3\right)=0\)

    \(y-3-\left(40-3\right)=0\)

    \(y-3-37=0\)

    \(y-\left(3+37\right)=0\)

    \(y-40=0\)

    \(y=0+40\)

    \(y=40\)

\(b)\left(7x13+8x13\right):\left(9\frac{2}{3}-y\right)=39\)

      \(\left(91+104\right):\left(\frac{29}{3}-y\right)=39\)

        \(195:\left(\frac{29}{3}-y\right)=39\)

         \(\frac{29}{3}-y=195:39\)

          \(\frac{29}{3}-y=5\)

            \(y=\frac{29}{3}-5\)

            \(y=\frac{14}{3}\)

Trả lời:

Áp dụng Bất Đẳng Thức Cauchy-Schwarz ta có:

(3+1)(3x2+y2)≥(3x+y)2

⇒4(3x2+y2)≥(3x+y)2⇒4(3x2+y2)≥(3x+y)2

⇒4(3x2+y2)≥(3x+y)2=12=1⇒4(3x2+y2)≥(3x+y)2=12=1

⇒M=3x2+y2≥14⇒M=3x2+y2≥14

Đẳng thức xảy ra khi x=y=14

Ta có:  x + y = 1 => y = 1 - x

Khi đó: P = \(x^3+y^3+2x^2y^2=\left(x+y\right)^3-3xy\left(x+y\right)+2\left(xy\right)^2\)

\(=2\left(xy\right)^2-3xy+1=2\left[\left(xy\right)^2-2.xy.\frac{3}{4}+\frac{9}{16}\right]-\frac{1}{8}\)

\(=2\left(xy-\frac{3}{4}\right)^2-\frac{1}{8}\)

\(=2\left[x\left(1-x\right)-\frac{3}{4}\right]^2-\frac{1}{8}\)

\(=2\left[-x^2+x-\frac{3}{4}\right]^2-\frac{1}{8}\)

\(=2\left[\left(x-\frac{1}{2}\right)^2+\frac{1}{2}\right]^2-\frac{1}{8}\ge\frac{3}{8}\)

Dấu "=" xảy ra <=> x = y =1/2

Thiếu: 

Kết luận: Vậy GTNN của P = 3/8 đạt tại x = y = 1/2.

Ta có : \(\frac{x}{5}=\frac{y}{7}=\frac{z}{3}\)

\(\Rightarrow\left(\frac{x}{5}\right)^2=\left(\frac{y}{7}\right)^2=\left(\frac{z}{3}\right)^2=\frac{x^2}{5^2}=\frac{y^2}{7^2}=\frac{z^2}{3^2}\)\(=\frac{x^2}{25}=\frac{y^2}{49}=\frac{z^2}{9}=\frac{x^2+y^2-z^2}{25+49-9}=\frac{585}{65}=9\)

\(\Rightarrow x=9.5=45\)

     \(y=9.7=63\)

     \(z=9.3=27\)

\(\Leftrightarrow\frac{4}{9}x^2=\frac{9}{16}y^2=\frac{25}{36}z^2\)

\(\Leftrightarrow\frac{900}{2025}x^2=\frac{900}{1600}y^2=\frac{900}{1296}z^2\)

Áp dụng t/c dãy tỉ số bằng nhau ta được:\(\Leftrightarrow\frac{900}{2025}x^2=\frac{900}{1600}y^2=\frac{900}{1296}z^2=\frac{900.\left(x^2+y^2+z^2\right)}{2025+1600+1296}=\frac{900.724}{4921}\)

=> x ~ 17,26; y ~ 15,34; z ~ 13,81.

Y x 4 + y x 3 + y = 720

Y x 4 + y x 3 + y x 1 = 720

y x (4 + 3 + 1) = 720
y x 8 = 720

y = 720 : 8

y = 90

cậu muốn gì hả Kurama

25.35.4

=25.4.35

=100.35

=3500

5.15.2

=5.2.15

=10.15

=150

x-9=0

    x=0+9

    x=9

x+10=10

      x=10-10

      x=0

25. 35 . 4 = ( 25 . 4 )  .35 = 100 . 35 = 3500

5 . 15 . 2 = ( 5 . 2 ) . 15 = 10 . 15= 150

Bài 2 : 

x - 9 = 0 => x = 0 + 9  => x = 9. Vậy x = 9

x + 10 = 10 => x = 10 - 10 => x = 0. Vậy x = 0