\(\left(x+4\right)^2-\left(x+1\right)\left(x+1\right)=16.\)

\(\Leftrightarrow x^2+8x+16-x^2-2x-1=16.\)

\(\Leftrightarrow6x+15=16.\Leftrightarrow x=\dfrac{1}{6}.\)

\(3x=2y=7z\)

⇒\(\dfrac{x}{14}=\dfrac{y}{21}=\dfrac{z}{6}\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có:

\(\dfrac{x}{14}=\dfrac{z}{6}=\dfrac{x-z}{14-6}=\dfrac{16}{8}=2\)

⇒\(\left\{{}\begin{matrix}x=14.2=28\\y=21.2=42\\z=6.2=12\end{matrix}\right.\)

C

G(-2)=0

=>4a+8+16=0

=>4a=-24

hay a=-6

đặt g(-2) = 0

=> a.(-2)² - 4.(-2) + 16 = 0

<=> 4a + 8 + 16 = 0

<=> 4a = -24

<=> a = -6

vậy để x = -2 là nghiệm của g(x) thì a = -6

G(-2)=0

=>4a+8+16=0

=>4a=-24

hay a=-6

\(32\times25+18\times100-50\times12\)

\(=800+1800-600\)

\(=2000\)

\(56\times45+28\times98+56\times6\)

\(=2520+2744+336\)

\(=5600\)

32 x 25 + 18 x 100 - 50 x 12 = 32 x 25 + 18 x 4 x 25 - 25 x 2 x 12

                                              = 32 x 25 + 72 x 25 - 25 x 24

                                              = ( 32 + 72 - 24 ) x 25

                                              = 80 x 25

                                              = 2000

56 x 45 + 28 x 98 + 56 x 6 = 56 x 45 + 28 x 2 x 49 + 56 x 6

                                          = 56 x 45 + 56 x 49 + 56 x 6

                                          = 56 x ( 45 + 49 + 6 )

                                          = 56 x 100

                                          = 5600

\(\frac{32x25+18x100-50x12}{56x45+28x98+56x6}\)

\(=\frac{800+1800-600}{2520+2744+336}\)

\(=\frac{2000}{5600}=\frac{5}{14}\)

~~~~~~~~~~~~~~~

\(2\left(x+56\right)\left(x-6\right)=3^{25}:3^{22}\)

\(\Rightarrow2\left(x+56\right)\left(x-6\right)=3^{25-22}\)

\(\Rightarrow2\left(x+56\right)\left(x-6\right)=3^3\)

\(\Rightarrow\left(x+56\right)\left(x-6\right)=\dfrac{27}{2}\)

\(\Rightarrow x^2-6x+56x-336=\dfrac{27}{2}\)

\(\Rightarrow x^2+50x-336=\dfrac{27}{2}\)

\(\Rightarrow x^2+50x+625-961=\dfrac{27}{2}\)

\(\Rightarrow\left(x+25\right)^2=\dfrac{27}{2}+961\)

\(\Rightarrow\left(x+25\right)^2=\dfrac{1949}{2}\)

\(\Rightarrow\left[{}\begin{matrix}x+25=\sqrt{\dfrac{1949}{2}}\\x+25=-\sqrt{\dfrac{1949}{2}}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{\dfrac{1949}{2}}-25\\x=-\sqrt{\dfrac{1949}{2}}-25\end{matrix}\right.\)

`(25-x)/56 = 6/16`

`=> (25-x)xx16= 56xx6`

`=> (25-x)xx16= 336`

`=> 25-x=336:16`

`=> 25-x=21`

`=>x=25-21`

`=>x=4`

`(25 - x)/56 = 6/16`

`=> (25 - x)/56 = 3/8`

`=> (25 - x)/56 = 21/56`

`=> 25  -x = 21`

`=> x = 25 - 21`

`=> x = 4`

Vậy `x = 4`

suy ra           x/56 =25-6/16

\(x=\left(25-\dfrac{6}{16}\right).56=1379\)