# 4.3: تقييم الدالة

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عندما يتم تقييم دالة، استبدل x بقيمة رقمية معينة أو تعبير جبري، ثم قم بتبسيط النتيجة.

##### مثال ParseError: invalid ArgList (click for details)Callstack: at (اللغة_العربية/(__)/04:_الوظائف/4.03:_تقييم_الدالة), /content/body/section[1]/header/div/h5/span/span, line 1, column 17 

إذا$$f(x) = −x^2 + 5x + 12$$، ابحث عن كل مما يلي:

1. $$f(2)$$
2. $$f(−5)$$
3. $$f(t)$$
4. $$f(4x − 1)$$
###### الحل
1. استبدل$$x$$ بـ$$2$$:

\begin{aligned} f(x)& = −x^ 2 + 5x + 12 && \text{Given equation} \\f(2) &= −(2^2 ) + 5 ∗ 2 + 12 && \text{Replace x with 2 - notice that only 2 is squared, not the minus sign} \\ f(2) &= −4 + 10 + 12 &&\text{Simplify} \\ f(2)& = 18 &&\text{Solution}\end{aligned}

1. استبدل$$x$$ بـ$$-5$$:

\begin{aligned} f(x) &= −x ^2 + 5x + 12 &&\text{Given equation } \\ f(−5) &= −((−5)^2 ) + 5 ∗ (−5) + 12 &&\text{Replace x with −5 - notice that it’s }−x ^2 \text{ , so the −5 is squared, but the result is still negative} \\ f(2) &= −25 + (−25) + 12 && \text{Simplify } \\ f(2) &= −38 &&\text{Solution} \end{aligned}

1. استبدل$$x$$ بـ$$t$$:

\begin{aligned} f(x) &= −x^2 + 5x + 12 &&\text{Given equation } \\ f(t)& = −t ^2 + 5 ∗ (t) + 12 && \text{Replace x with t } \\ f(t) &= −t 2 + 5t + 12&& \text{Simplify } \end{aligned}

1. استبدل$$x$$ بـ$$(4x-1)$$:

\begin{aligned} f(x) &= −x^2 + 5x + 12&& \text{Given equation} \\ f(4x − 1) &= −(4x − 1)^2 + 5 ∗ (4x − 1) + 12 &&\text{Replace x with }(4x - 1) \\ f(4x − 1) &= −(16x ^2 − 8x + 1) + 20x − 5 + 12 &&\text{Expand} (4x − 1)^2 \text{ and distribute the }5 \text{ to } (4x - 1) \\ f(4x − 1) &= −16x^ 2 + 8x − 1 + 20x − 5 + 12 && \text{Distribute the negative sign}\\ f(4x − 1) &= 16x ^2 + 28x + 6 && \text{Simplify} \end{aligned}

##### التمرين ParseError: invalid ArgList (click for details)Callstack: at (اللغة_العربية/(__)/04:_الوظائف/4.03:_تقييم_الدالة), /content/body/section[2]/header/div/h5/span/span, line 1, column 17 
1. للحصول على الوظيفة$$f(x) = x^3 − 9$$، ابحث
1. $$f(3)$$
2. $$f(2x-5)$$
3. $$f(t)$$
2. للحصول على الوظيفة$$f(x) = x^2 − 4x + 1$$، ابحث
1. $$f(2)$$
2. $$f(4x+3)$$
3. $$f(z)$$
3. للحصول على الوظيفة$$f(x) = x^4 + 9x^2 − 6x − 1$$، ابحث
1. $$f(1)$$
2. $$f(x+2)$$
3. $$f(a)$$