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a) f(-2)=5 – 2. (-2) = 5 + 4 = 9;
f(-1) = 5 – 2.(-1) = 5 + 2 = 7;
f(0) = 5 – 2.0 = 5;
f(3) = 5 – 2.3 = 5 – 6 = -1.
b)\(y=5-2x\Rightarrow x=\dfrac{5y}{2}\)
\(y=5\Rightarrow x=\dfrac{5-5}{2}=0\)
\(y=3\Rightarrow x=\dfrac{5-3}{2}=1\)
\(y=-1\Rightarrow x=\dfrac{5-\left(-1\right)}{2}=\dfrac{5+1}{2}=3\)
\(\text{1)}\)
\(\text{Thay }x=-2,\text{ ta có: }f\left(-2\right)-5f\left(-2\right)=\left(-2\right)^2\Rightarrow f\left(-2\right)=-1\)
\(\Rightarrow f\left(x\right)=x^2+5f\left(-2\right)=x^2-5\)
\(f\left(3\right)=3^2-5\)
\(\text{2)}\)
\(\text{Thay }x=1,\text{ ta có: }f\left(1\right)+f\left(1\right)+f\left(1\right)=6\Rightarrow f\left(1\right)=2\)
\(\text{Thay }x=-1,\text{ ta có: }f\left(-1\right)+f\left(-1\right)+2=6\Rightarrow f\left(-1\right)=2\)
\(\text{3)}\)
\(\text{Thay }x=2,\text{ ta có: }f\left(2\right)+3f\left(\frac{1}{2}\right)=2^2\text{ (1)}\)
\(\text{Thay }x=\frac{1}{2},\text{ ta có: }f\left(\frac{1}{2}\right)+3f\left(2\right)=\left(\frac{1}{2}\right)^2\text{ (2)}\)
\(\text{(1) - 3}\times\text{(2) }\Rightarrow f\left(2\right)+3f\left(\frac{1}{2}\right)-3f\left(\frac{1}{2}\right)-9f\left(2\right)=4-\frac{1}{4}\)
\(\Rightarrow-8f\left(2\right)=\frac{15}{4}\Rightarrow f\left(2\right)=-\frac{15}{32}\)
4. (3/4-81)(3^2/5-81)(3^3/6-81)....(3^6/9-81).....(3^2011/2014-81)
mà 3^6/9-81=0 => (3/4-81)(3^2/5-81)....(3^2011/2014-81)=0
a) \(y=f\left(x\right)=-\frac{1}{2}x\)
\(f\left(-2\right)=-\frac{1}{2}.\left(-2\right)=1\)
\(f\left(3\right)=-\frac{1}{2}.3=-\frac{3}{2}\)
b)
Cho \(x=1\Rightarrow y=-\frac{1}{2}.1=-\frac{1}{2}\)
\(\Rightarrow A\left(1;-\frac{1}{2}\right)\)
O 1 2 1 2 -1 -2 -1 -2 -1/2 A y=-1/2x
Hình ko đẹp lắm mong cậu thông cảm
a). x = -5 => y = 5.(-5)-1 = -26 => y = -26
x = -4 => y = 5.(-4)-1 = -21 => y = -21
x = -3 => y = 5.(-3)-1 = -16 => y = -16
x = -2 => y = 5.(-2)-1 = -11
x = 0 => y = 5.0-1 = -1
x = \(\frac{1}{5}\) => y = 5.\(\frac{1}{5}\)-1 = 0 => y = 0
*Vậy các giá trị tương ứng của y là: -26 ; -21 ; -16 ; -11 ; -1 ; 0.
b). y = f ( \(\frac{1}{2}\)) = 3.( \(\frac{1}{2}\))2 + 1 = \(\frac{7}{4}\)=> f (\(\frac{1}{2}\)) = \(\frac{7}{4}\)
y = f (1) = 3.12 + 1 = 4 => f (1) = 4
y = f (3) = 3.32 + 1 = 28 => f (3) = 28.
(Bài này mình tự làm. Chúc bạn học tốt môn Math ^^)