Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
A=|x+1/2|-|x+2|+x-3/4|
=|-1/2+1/2|-|-1/2+2|+|-1/2-3/4|
=0-3/2+5/4
= -1/4
\(a,f\left(1\right)=3\cdot1^2+1+1=5\\ f\left(-\dfrac{1}{3}\right)=3\cdot\left(-\dfrac{1}{3}\right)^2-\dfrac{1}{3}+1=\dfrac{1}{3}-\dfrac{1}{3}+1=1\\ f\left(\dfrac{2}{3}\right)=3\cdot\left(\dfrac{2}{3}\right)^2-\dfrac{2}{3}+1=\dfrac{4}{3}-\dfrac{2}{3}+1=\dfrac{5}{3}\\ f\left(-2\right)=3\cdot\left(-2\right)^2-2+1=11\\ f\left(-\dfrac{4}{3}\right)=3\cdot\left(-\dfrac{4}{3}\right)^2-\dfrac{4}{3}+1=\dfrac{16}{3}-\dfrac{4}{3}+1=5\)
\(b,f\left(\dfrac{2}{3}\right)=\left|2\cdot\dfrac{2}{3}-9\right|-3=\dfrac{23}{3}-3=\dfrac{14}{3}\\ f\left(-\dfrac{5}{4}\right)=\left|2\cdot\left(-\dfrac{5}{4}\right)-9\right|-3=\dfrac{23}{2}-3=\dfrac{17}{2}\\ f\left(-5\right)=\left|2\left(-5\right)-9\right|-3=19-3=16\\ f\left(4\right)=\left|2\cdot4-9\right|-3=1-3=-2\\ f\left(-\dfrac{3}{8}\right)=\left|2\cdot\left(-\dfrac{3}{8}\right)-9\right|-3=\dfrac{39}{4}-3=\dfrac{27}{4}\)
\(c,x=0\Rightarrow y=2\cdot0^2-7=-7\\ x=-3\Rightarrow y=2\cdot\left(-3\right)^2-7=11\\ x=-\dfrac{1}{2}\Rightarrow y=2\cdot\left(-\dfrac{1}{2}\right)^2-7=\dfrac{-13}{2}\\ x=\dfrac{2}{3}\Rightarrow y=2\cdot\left(\dfrac{2}{3}\right)^2-7=-\dfrac{55}{9}\)
\(A=\left|-\dfrac{1}{2}+\dfrac{1}{2}\right|-\left|-\dfrac{1}{2}+2\right|+\left|-\dfrac{1}{2}-\dfrac{3}{4}\right|=-\dfrac{3}{2}+\dfrac{5}{4}=\dfrac{5}{4}-\dfrac{6}{4}=\dfrac{-1}{4}\)
Ta có:
Tại x = -1/2 thì giá trị của biểu thức là:
\(\left|-\frac{1}{2}+\frac{1}{2}\right|-\left|-\frac{1}{2}+2\right|+\left|-\frac{1}{2}-\frac{3}{4}\right|\)
\(=\left|0\right|-\left|\frac{3}{2}\right|+\left|-\frac{5}{4}\right|\)
\(=0-\frac{3}{2}+\frac{5}{4}\)
\(=-\frac{1}{4}\)