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TM
1
25 tháng 12 2021
Cho hàm số y=f(x)= −3x.
Ta có f(\(\dfrac{-3}{2}\)) = -3. (\(\dfrac{-3}{2}\))
= \(\dfrac{-3.\left(-3\right)}{2}\)
=\(\dfrac{9}{2}\)
Ta có f(-1) = -3. (-1)
= 3
Vậy f(\(\dfrac{-3}{2}\)) = \(\dfrac{9}{2}\) và f(-1) = 3.
KB
1
LH
18 tháng 4 2017
Ta có y = f(x) = 3x2 + 1. Do đó
f(\(\dfrac{1}{2}\)) = 3.\(\left(\dfrac{1}{2}\right)^2\) + 1 = \(\dfrac{3}{4}\)+ 1 = \(\dfrac{7}{4}\)
f(1) = 3.12 + 1 = 3.1 + 1 = 3 + 1 = 4
f(3) = 3.32 + 1 = 3.9 + 1 = 27 + 1 = 28.
20 tháng 2 2021
(1)
a) x=\(\dfrac{-1}{12}-\dfrac{2}{3}\)=\(\dfrac{-3}{4}\)
b) 2x+1=3 => 2x=3-1=2 => x=1
(2)
f(2)=2.22+4=12
f(-1)=2.(-1)2+4=6
20 tháng 2 2021
(1)
a) \(x+\dfrac{2}{3}=-\dfrac{1}{12}\\ \Rightarrow x=-\dfrac{1}{12}-\dfrac{2}{3}\\ \Rightarrow x=\dfrac{-1}{12}-\dfrac{8}{12}\\ \Rightarrow x=-\dfrac{9}{12}=-\dfrac{3}{4}\)
Vậy \(x=-\dfrac{3}{4}\)
b) \(\left(2x+1\right)^2=9\\ \Rightarrow\left(2x+1\right)^2=3^2=\left(-3\right)^2\\ \Rightarrow\left[{}\begin{matrix}2x+1=3\\2x+1=-3\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}2x=2\\2x=-4\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)
Vậy \(x\in\left\{-2;1\right\}\)
(2)
\(y=f\left(x\right)=2x^2+4\\ f\left(2\right)=2\cdot2^2+4=8+4=12\\ f\left(-1\right)=2\cdot\left(-1\right)^2+4=2+4=6\)
Vậy \(f\left(2\right)=12\\ f\left(-1\right)=6\)
ML
30 tháng 6 2015
\(\text{1)}\)
\(\text{Thay }x=-2,\text{ ta có: }f\left(-2\right)-5f\left(-2\right)=\left(-2\right)^2\Rightarrow f\left(-2\right)=-1\)
\(\Rightarrow f\left(x\right)=x^2+5f\left(-2\right)=x^2-5\)
\(f\left(3\right)=3^2-5\)
\(\text{2)}\)
\(\text{Thay }x=1,\text{ ta có: }f\left(1\right)+f\left(1\right)+f\left(1\right)=6\Rightarrow f\left(1\right)=2\)
\(\text{Thay }x=-1,\text{ ta có: }f\left(-1\right)+f\left(-1\right)+2=6\Rightarrow f\left(-1\right)=2\)
\(\text{3)}\)
\(\text{Thay }x=2,\text{ ta có: }f\left(2\right)+3f\left(\frac{1}{2}\right)=2^2\text{ (1)}\)
\(\text{Thay }x=\frac{1}{2},\text{ ta có: }f\left(\frac{1}{2}\right)+3f\left(2\right)=\left(\frac{1}{2}\right)^2\text{ (2)}\)
\(\text{(1) - 3}\times\text{(2) }\Rightarrow f\left(2\right)+3f\left(\frac{1}{2}\right)-3f\left(\frac{1}{2}\right)-9f\left(2\right)=4-\frac{1}{4}\)
\(\Rightarrow-8f\left(2\right)=\frac{15}{4}\Rightarrow f\left(2\right)=-\frac{15}{32}\)
4 tháng 2 2021
\(f\left(-1\right)=2\Rightarrow-a+b-c+d=2\\ f\left(0\right)=1\Rightarrow d=1\\ f\left(1\right)=7\Rightarrow a+b+c+d=7\\ f\left(\dfrac{1}{2}\right)=3\Rightarrow\dfrac{1}{8}a+\dfrac{1}{4}b+\dfrac{1}{2}c+d=3\)
\(d=1\Rightarrow-a+b-c=1;a+b+c=6\\ \Rightarrow2b=7\\ \Rightarrow b=\dfrac{7}{2}\\ \Rightarrow\dfrac{1}{8}a+\dfrac{7}{8}+\dfrac{1}{2}c=2\\ \Rightarrow\dfrac{1}{2}\left(\dfrac{1}{4}a+\dfrac{7}{4}+c\right)=2\\ \Rightarrow\dfrac{1}{4}a+\dfrac{7}{4}+c=4\\ \Rightarrow a+7+4c=16\\ \Rightarrow a+4c=9;a+c=6-\dfrac{7}{2}=\dfrac{5}{2}\\ \Rightarrow3c=\dfrac{13}{2}\Rightarrow c=\dfrac{13}{6}\\ \Rightarrow a=\dfrac{5}{2}-\dfrac{13}{6}=\dfrac{1}{3}\)
Vậy \(\left(a;b;c;d\right)=\left(\dfrac{1}{3};\dfrac{7}{2};\dfrac{13}{6};1\right)\)
VC
Vũ Cao Minh⁀ᶦᵈᵒᶫ ( ✎﹏IDΣΛ亗 )
CTV
VIP
13 tháng 12 2019
Ta có : \(y=f\left(x\right)=2x^2-3x+1\)
\(f\left(-1\right)=2\left(-1\right)^2-3.\left(-1\right)+1=2.1-\left(-3\right)+1=2+3+1=6\)
\(f\left(2\right)=2.2^2-3.2+1=2.4-6+1=8-6+1=3\)
\(f\left(\frac{-1}{2}\right)=2\left(\frac{1}{2}\right)^2-3.\frac{1}{2}+1=2.\frac{1}{4}-\frac{3}{2}+1=\frac{1}{2}-\frac{3}{2}+\frac{2}{2}=0\)
19 tháng 12 2021
\(a,f\left(-\dfrac{1}{2}\right)=\dfrac{1}{4}+4=\dfrac{17}{4}\\ f\left(5\right)=25+4=29\\ b,f\left(x\right)=10=x^2+4\Leftrightarrow x^2=6\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{6}\\x=-\sqrt{6}\end{matrix}\right.\)
Ta có hàm số sau :
\(f\left(1\right)=3.1^2-1=2\)
\(f\left(\frac{-2}{3}\right)=3.\frac{-2}{3}-1=-2-1=-3\)
Vậy hàm số f(1) = 2
Hàm số :\(f\left(\frac{-2}{3}\right)=-3\)