a: f(-2)=-6+1=-5

f(1/2)=3/2+1=5/2

      Giải:

Bài 1: lần lượt thay các giá trị của x, ta có:

_Y=f(-1)= -5.(-1)-1=4

_Y=f(0)= -5.0-1=1

_Y=f(1)= -5.1-1=-6

_Y=f(1/2)= -5.1/2-1=-7/2

Bài 2: 

a: f(-2)=7

f(-1)=5

f(0)=3

a)\(f\left(1\right)=2.1^2+5.1-3=2+5-3=4\)

\(f\left(0\right)=0+0-3=-3\)

\(f\left(1,5\right)=2.\left(1,5\right)^2-5.1,5-3=4,5-7,5-3=-6\)

b)\(f\left(3\right)=3a-3=9=>>3a=12=>a=4\)

\(f\left(5\right)=5a-3=11=>5a=14=>a=\dfrac{14}{5}\)

\(f\left(-1\right)=-a-3=6=>-a=9=>a=-9\)

`a)`

`@f(1)=2.1^2+5.1-3=2.1+5-3=2+5-3=4`

`@f(0)=2.0^2+5.0-3=-3`

`@f(1,5)=2.(1,5)^2+5.1,5-3=4,5+7,5-3=9`

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`b)`

`***f(3)=9`

`=>3a-3=9`

`=>3a=12=>a=4`

`***f(5)=11`

`=>5a-3=11`

`=>5a=14=>a=14/5`

`***f(-1)=6`

`=>-a-3=6`

`=>-a=9=>a=-9`

a: f(1)=2+5-3=4

f(0)=-3

f(1,5)=4,5+7,5-3=9

b: f(3)=9 nên 3a-3=9

hay a=4

f(5)=11 nên 5a-3=11

hay a=14/5

f(-1)=6 nên -a-3=6

=>-a=9

hay a=-9

\(a,f\left(-1\right)=\left(-5\right)\left(-1\right)-3=5-3=2\\ f\left(\dfrac{2}{3}\right)=-5.\dfrac{2}{3}-3=\dfrac{-10}{3}-3=-\dfrac{19}{3}\)

\(b,y=-8\Rightarrow-8=-5x-3\Rightarrow-5=-5x\Rightarrow x=1\\ y=6\Rightarrow6=-5x-3\Rightarrow9=-5x\Rightarrow x=-\dfrac{9}{5}\)

a: f(-1)=5-3=2

f(2/3)=-10/3-3=-19/3

b: y=-8 

=>-5x-3=-8

=>-5x=-5

hay x=1

y=6

=>-5x-3=6

=>-5x=9

hay x=-9/5

\(f\left(x\right)=x^2-5x+6\)

a) +) \(f\left(-\frac{1}{3}\right)=\left(-\frac{1}{3}\right)^2-5.\left(-\frac{1}{3}\right)+6=\frac{70}{9}\)

+) \(f\left(\frac{1}{2}\right)=\left(\frac{1}{2}\right)^2-5.\frac{1}{2}+6=\frac{15}{4}\)

+) \(f\left(0\right)=0^2-5.0+6=6\)

+) \(f\left(1\right)=1^2-5.1+6=2\)

b) \(x^2-5x+6=0\)

\(\Leftrightarrow\left(x-2\right)\left(x-3\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\x-3=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=2\\x=3\end{cases}}\)

ok

\(f\left(3\right)=3a-3=9\)

\(3a=12\Rightarrow a=4\)

\(f\left(5\right)=5a-3=11\)

\(5a=14\Rightarrow a=\dfrac{14}{5}\)

\(f\left(-1\right)=-a-3=6\)

\(-a=9\Rightarrow a=9\)

a) \(f\left(x\right)=2x^2+5x-3\)

\(f\left(1\right)=2.1^2+5.1-3=2+5-3=4\)

\(f\left(0\right)=-3\)

\(f\left(1,5\right)=2.\left(1,5\right)^2+5.1,5-3=2.2,25+7,5-3=9\)

\(f\left(-1\right)=-5\left(-1\right)-1=5-1=4\\ f\left(0\right)=-5.0-1=-1\\ f\left(1\right)=-5.1-1=-5-1=-6\\ f\left(\dfrac{1}{2}\right)=-5\left(\dfrac{1}{2}\right)-1=\dfrac{-5}{2}-1=\dfrac{-7}{2}\)

Ta có : \(f\left(-1\right)=-5\left(-1\right)-1=5-1=4\)

\(f\left(0\right)=-5.0-1=-1\)

\(f\left(1\right)=-5.1-1=-5-1=-6\)

\(f\left(\dfrac{1}{2}\right)=-\dfrac{5.1}{2}-1=-\dfrac{5}{2}-1=-\dfrac{7}{2}\)

f(-1)=-5.-1+3=5+3=8

f(0)=-5.0+3=0+3=3

f(3)=-5.3+3=-15+3=-12

f(-1)=-5.(-1)+3=5+3=8

f(0)=-5.0+3=0+3=3

f(3)=-5.3+3=-15+3=-12

\(f\left(x\right)=2x^2+5x-3\)

f(1)=2+5-3=4

f(0)=-3

f(1,5)=2x2,25+5x1,5-3=9

\(f\left(x\right)=2x^2+5x-3\)

\(f\left(1\right)=2.1^2+5.1-3=2+5-3=4\)

\(f\left(0\right)=-3\)

\(f\left(1,5\right)-2.\left(1,5\right)^2+5.1,5-3=9\)

f(x) = 2x² + 5x -3

f(1) = 2.1² + 5.1 - 3 = 2.1 + 5.1 - 3 = 4

f(0) = 2.0² + 5.0 - 3 = -3

f(1,5) = 2 . 1,5² + 5 . 1,5 - 3 = 9