bang 202

a = 3

b = 0

giúp mik với

20+20+20=60

Ta có: 3/4 . x = 1/12 + 3/8

<=> 3/4 x = 8/96 + 36/96

<=> 3/4 x = 44/96

<=> 3/4 x = 11/24

<=> x = 11/24 : 3/4

<=> x = 11/24 . 4/3

<=> x = 11/18

Vậy x = 11/18.

tuổi mẹ 3 năm trước là : 32 : ( 7 - 3 ) x 7 = 56 ( t u ổ i )

tuổi mẹ hiện nay là : 56 + 3 = 59 ( t u ổ i )

tuổi con hiện nay là : 59 - 32 = 27 ( t u ổ i )

đáp số : mẹ : 59 tuổi

             con : 27 tuổi

\(\left(x-1\right)\left(x+2\right)-x-2=0\)

\(\Leftrightarrow\left(x-1\right)\left(x+2\right)-\left(x+2\right)=0\)

\(\Leftrightarrow\left(x+2\right)\left(x-2\right)=0\Leftrightarrow x=\pm2\)

\(\left(x-1\right)\left(x-3\right)\left(x-4\right)\left(x-6\right)+10\)

\(=\left(x-1\right)\left(x-6\right)\left(x-3\right)\left(x-4\right)+10\)

\(=\left(x^2-6x-x+6\right)\left(x^2-4x-3x+12\right)+10\)

\(=\left(x^2-7x+9-3\right)\left(x^2-7x+9+3\right)+10\)

\(=\left(x^2-7x+9\right)^2-9+10=\left(x^2-7x+9\right)^2+1\ge1\)

\("="\Leftrightarrow x^2-7x+9=0\)

\(\Leftrightarrow x^2-7x+\dfrac{49}{4}-\dfrac{13}{4}=0\)

\(\Leftrightarrow\left(x-\dfrac{7}{2}+\sqrt{\dfrac{13}{4}}\right)\left(x-\dfrac{7}{2}-\sqrt{\dfrac{13}{4}}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{2}-\sqrt{\dfrac{13}{4}}\\x=\dfrac{7}{2}+\sqrt{\dfrac{13}{4}}\end{matrix}\right.\)

\(VT=\left(a+b\right)\left(a+c\right)+\left(a+c\right)\left(c+b\right)=\left(a+c\right)\left(a+b+c+b\right)=\left(a+c\right)\left(a+c+2b\right)\)

\(=\left(a+c\right)^2+2b\left(a+c\right)=a^2+2ac+c^2+2ab+2bc=2b^2+2ac+2ab+2bc\)

\(VP=2\left(a+b\right)\left(b+c\right)=2ab+2ac+2b^2+2bc\)

\(\Leftrightarrow VT=VP\left(đpcm\right)\)