f(x) = 2x^3 + x^2 - 5x + c, where c is a constant - Edexcel - A-Level Maths Pure - Question 3 - 2006 - Paper 2
Question 3
f(x) = 2x^3 + x^2 - 5x + c, where c is a constant.
Given that f(1) = 0,
(a) find the value of c.
(b) factorise f(x) completely,
(c) find the remainder when f(x) ... show full transcript
Worked Solution & Example Answer:f(x) = 2x^3 + x^2 - 5x + c, where c is a constant - Edexcel - A-Level Maths Pure - Question 3 - 2006 - Paper 2
Step 1
(a) find the value of c
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Answer
To find the value of c, we substitute x = 1 into the function:
f(1) = 2(1)^3 + (1)^2 - 5(1) + c = 0$$
This simplifies to:
2 + 1 - 5 + c = 0 \
-2 + c = 0 \
c = 2
Step 2
(b) factorise f(x) completely
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Answer
Given:
f(x)=2x3+x2−5x+2
To factorise, we can first factor out common terms using synthetic division, dividing by (x - 1):
Upon performing synthetic division, we find:
f(x)=(x−1)(2x2+3x−2)
Now we need to factor the quadratic expression:
2x2+3x−2=(2x−1)(x+2)
Thus, the complete factorization is:
f(x)=(x−1)(2x−1)(x+2)
Step 3
(c) find the remainder when f(x) is divided by (2x - 3)
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Answer
To find the remainder when dividing f(x) by (2x - 3), we can use the Remainder Theorem. We first need to find the value of x where 2x - 3 = 0: