Toán cho hàm số y=f(x)=2x^2+2x-7 chứng minh f(a)-f(b) = 2(a^2-b^2)+3(a-b) 04/12/2021 By Alaia cho hàm số y=f(x)=2x^2+2x-7 chứng minh f(a)-f(b) = 2(a^2-b^2)+3(a-b)
Ta có: $f(x) = 2x^2 + 2x – 7$ $\to \begin{cases}f(a) = 2a^2 + 2a – 7\\f(b) = 2b^2 + 2b – 7\end{cases}$ $\to f(a) – f(b) = (2a^2 + 2a- 7)-(2b^2+ 2b – 7)$ $\to f(a) – f(b) = 2(a^2 – b^2) + 2(a-b)$ Trả lời
Ta có:
$f(x) = 2x^2 + 2x – 7$
$\to \begin{cases}f(a) = 2a^2 + 2a – 7\\f(b) = 2b^2 + 2b – 7\end{cases}$
$\to f(a) – f(b) = (2a^2 + 2a- 7)-(2b^2+ 2b – 7)$
$\to f(a) – f(b) = 2(a^2 – b^2) + 2(a-b)$