Suppose p ( x ) = a x 2 + b x + c is a quadratic polynomial satisfying p ( 7 ) − p ( 3 ) = 2 1 4 . Determine the value of p ( 9 ) − p ( 1 ) .
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hey look its william
this whole problem may as well have been made without c i do not know why you even mention it in your proof.
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I mention it because it may not be obvious to some why the equations are true; it is less confusing.
I ignored this entirely:
p ( x ) = a x 2 + b x + c
p ( 7 ) − p ( 3 ) = 2 1 4 p ( 7 ) − p ( 3 ) = p ( 4 ) Therefore...
p ( 4 ) = 2 1 4
p ( 9 ) − p ( 1 ) = p ( 8 )
p ( 4 ) × 2 = p ( 8 )
Therefore...
p ( 8 ) = 2 1 4 × 2 = 4 2 8
So the answer is 428 .
As pointed out by Chee, this solution is wrong.
Let's put your solution aside, now, can you prove that p ( x ) − p ( y ) = p ( x − y ) such that both p ( x ) and p ( y ) are polynomials? None of them! You have to know that p ( x ) is a function, just like the f ( x ) in the previous problem sets, and not a variable. If p ( x ) is a variable, then it should be written as p x not p ( x ) .
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As pointed out by Chee, your solution is incorrect. p ( x ) is a function. p is not a constant.
From the question, we can say
p ( 7 ) − p ( 3 ) = 2 1 4
7 2 a + 7 b + c − ( 3 2 a + 3 b + c ) = 2 1 4
4 9 a + 7 b + c − ( 9 a + 3 b + c ) = 2 1 4
4 0 a + 4 b = 2 1 4
Then,
p ( 9 ) − p ( 1 )
= 9 2 a + 9 b + c − ( 1 2 a + 1 b + c )
= 8 1 a + 9 b + c − ( a + b + c )
= 8 0 a + 8 b
= 2 ( 4 0 a + 4 b )
= 2 ( 2 1 4 )
= 4 2 8
sry i still didnt understand
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May I know where you get confused? I will try my best to explain.
You may consider, if you wish, looking at my explanation. That may help you out.
1) We have p ( x ) = a x 2 + b x + c and p ( 7 ) − p ( 3 ) = 2 1 4 .
2) The value of p ( 7 ) , when x = 7 in p ( x ) = a x 2 + b x + c :
p ( 7 ) = 7 2 a + 7 b + c
⟹ 4 9 a + 7 b + c
3) And the value of p ( 3 ) , when x = 3 in p ( x ) = a x 2 + b x + c :
p ( 3 ) = 3 2 a + 3 b + c
⟹ 9 a + 3 b + c
4) Work out the value of p ( 7 ) − p ( 3 ) :
p ( 7 ) − p ( 3 ) = ( 4 9 a + 7 b + c ) − ( 9 a + 3 b + c )
⟹ 4 0 a + 4 b
⟹ 4 ( 1 0 a + b )
5) Putting the value of p ( 7 ) − p ( 3 ) = 2 1 4 :
p ( 7 ) − p ( 3 ) = 2 1 4
⟹ 4 ( 1 0 a + b ) = 2 1 4
⟹ 1 0 a + b = 4 2 1 4
6) We get the value of 1 0 a + b = 4 2 1 4
7) p ( 9 ) − p ( 1 ) should be [like step 2 or 3] :
p ( 9 ) − p ( 1 ) = ( 9 2 a + 9 b + c ) − ( 1 2 a + 1 . b + c )
⟹ ( 8 1 a + 9 b + c ) − ( a + b + c )
⟹ 8 0 a + 8 b
⟹ 8 ( 1 0 a + b )
8) Putting the value of 1 0 a + b = 4 2 1 4 [from step 6] :
p ( 9 ) − p ( 1 ) = 8 ( 1 0 a + b )
⟹ 8 × 4 2 1 4
⟹ 2 × 2 1 4 ⟹ 4 2 8
9) We get the value of p ( 9 ) − p ( 1 ) = 4 2 8
your write men ;)
i just came here to see what other answers were like, but now this website thinks this is my level and does not allow me level up.
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If you work through the Diagnostic (only once), that should update your level.
p(7) - p(3) = 40a + 4b
p(9) - p(1) = 80a + 8b
Since 80a + 8b is double 40a + 4b you just need to double 214 to get 428
Is my way is wrong ? P(7)-p(3) = 214 7p-3p = 214 9p-1p = ? 4p=214 8p=? p=107/2 8(107/2) = 428
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Yes bro.........this is a wrong method..........because "p" is a function in "x" and not a variable................so you can't write.......p(7)=7p......:)
p(7) = 49a + 7b + c and p(3) = 9a + 3b + c therefore, p(7) - p(3) = 40a + 4b = 214, and then p(9) = 81a + 9b + c and p(1) = a+b+c and p(9) - p(1) = 80a + 8b = 2(40a+4b) = 2(214) = 428
ang galing mo naman sa math , paturo naman po
If you plug 7 and 3 into the equation you get:
[a(49) - b(7) + c] - [a(9) + b(3) + c] = a(40) - b(4)
> If you do the same for P(9) - P(1)
You get: a(80) + b(8)
= 2 [ a(40) + b(4) ] = 2 * 214 = 428
By the definition we have that p ( 7 ) = 4 9 a + 7 b + c , and p ( 3 ) = 9 a + 3 b + c , so p ( 7 ) − p ( 3 ) = 4 0 a + 4 b = 4 ( 1 0 a + b ) = 2 1 4 . On the other hand we have p ( 9 ) = 8 1 a + 9 b + c , and p ( 1 ) = a + b + c , so p ( 9 ) − p ( 1 ) = 8 0 a + 8 b = 8 ( 1 0 a + b ) = 2 ( 4 ( 1 0 a + b ) ) . But 4 ( 1 0 a + b ) = 2 1 4 . Hence p ( 9 ) − p ( 1 ) = 2 ( 2 1 4 ) = 4 2 8 .
First off I looked for the constant value, the first thing that struck out was that it was the same function both times. I noted this and then inserted the variables into the equation giving; P(7)=49a+7b+c P(3)=9a+3b+c I then inserted these equations into the second equation giving; (49a+7b+c)-(9a+3b+c)=214 Solving gives; 40a+4b=214 I then did the same for the second set of values giving; 80a+8b=x Since it is the same function and we have a linear equation they are directly proportional, e.g if one doubles the other doubles which is what is happening here so; 1/2x=214 x=428
On solving p(7) - p(3), we arrive at the equation, 40a + 4b = 214. Now, to get to know more about the constants, we need at least two more equations. The present situation seems to be against this idea. So lets keep the deduced equation aside and try to solve p(9) - p(1). Now, on solving this, we end up at 80a + 8b, which is interestingly the double of (40a + 4b). Since we have already found out this value, we multiply it(i.e. 214 ) by 2 to get 428.
We have, p(7)-p(3)=(49a+7b+c)-(9a+3b+c)=40a+4b=214 (given)............................Then, p(9)-p(1)=(81a+9b+c)-(a+b+c)=80a+8b=2(40a+4b)=2*214=428.
Given: Quadratic Equation with variables a, b, c & x [Also p] Equation answering the quadratic given.
To Do: Simplify the equation p(7) - p(3) = 214 p(7-3) = 214 p(4) = 214 p = 214 / 4 p = 53.5 Now, Substitute the value of 'p' in the the next equation.
p(9) - p(1) = ? p(9 -1) = ? p(8) = ?
Substituting the value of 'p'
53.5 * 8 = 428
As pointed out by Chee, this solution is incorrect. p ( x ) is a function. p doesn't have a value of 53.5.
its help me so much . thanks
As pointed out by Chee above, your solution is wrong. p ( x ) is a function, and not the value of p × x .
We can write p ( 7 ) − p ( 3 ) = 2 1 4 as 4 9 a + 7 b + c − ( 9 a + 3 b + c ) = 2 1 4 . Simplifying, we get 4 0 a + 4 b = 2 1 4 . Now let's work with p ( 9 ) − p ( 1 ) . We can write p ( 9 ) − p ( 1 ) as 8 1 a + 9 b + c − ( a + b + c ) Simplifying, we get 8 0 a + 8 b . 8 0 a + 8 b is just 2 ⋅ ( 4 0 a + 4 b ) , and we can substitute 214 into 4 0 a + 4 b , so 8 0 a + 8 b = 4 2 8
nice
By inputting 7 and 3 as x we get:
( 4 9 a + 7 b + c ) − ( 9 a + 3 b + c ) = ( 4 0 a + 4 b )
By also inputting 9 and 1 we get:
( 8 1 a + 9 b + c ) − ( a + b + c ) = ( 8 0 a + 8 b )
This means that:
p ( 9 ) − p ( 1 ) = 2 ∗ ( p ( 7 ) − p ( 3 ) )
Since:
p ( 7 ) − p ( 3 ) = 2 1 4
p ( 9 ) − p ( 1 ) = 4 2 8
If p(7) - p(3) = 214 then
(49a + 7b + c) - (9a + 3b +c) = 214
40a + 4b = 214
p(9) - p(1) can be defined by the following expression which we'll call x
(81a +9b + c) - (a + b + c) = x
80a + 8b = x
Factoring we get
8(10a + b) = x
Factoring 40a + 4b we get 4(10a + b) = 214
Because 214/(10a + b) = 4 and x/(10a + b) = 8 we know that x must be twice as large as 214 so 428 is our answer
P(7) = 49a+7b+c
P(3) = 9a+3b+c
P(9) =81a+9b+c
P(1) = a+b+c
P(7)-P(3) = 49a+7b+c-9a-3b-c
= 40a+4b
therefore, 40a+4b=214 ----------------------(1)
P(9)-P(1) = 81a+9b+c-a-b-c
= 80a+8b
therefore, 80a+8b = k ----------------------(2)
Now, we have a system of equation to solve from (1) and (2)
40a+4b=214
80a+8b=k -------> divide by 2 --------> 40a+4b=k/2
So, 214 = k/2 -------------> k = 428
p(4) = 214
1# p(9) - p(1) = p(8) p(8) is two times the amount of p(4) or 214. 214 * 2 = 428
P(7)-P(3)= 49a+7b+c-9a-3b-c=40a+4b=214
P(9)-P(1)=81a+9b+c-a-b-c=80a+8b=2(40a+4b)=2*214=428
p(x) = a x 2 + bx + c
as we may know in the first case p(7) , x is equal to 7
substitute the value of x, so we obtain these equations
p(7) = 49a+7b+c
p(3) = 9a+3b+c
and then subtract p(3) from p(7),so we obtain that 40a+4b = 214
for the p(9) and p(1)
p(9) = 81a+9b+c
p(1) = a+b+c
then subtract p(1) from p(9) ,we will then obtain 80a+8b
if 40a+4b = 214
80a+8b can be simplified to this form 2(40a+4b)
that is the same to 2(214)
so the value of 80a+80b is 4 2 8
p(7)-p(3)= 49a+7b+c - (9a+3b+c) = 40a+4b=214 (I)
p(9)-p(1)= 81a+9b+c - (a+b+c) = 80a+ 8b (II)
So, it´s easy to see that if you multiply (I) by 2, it´s (II).
Finally you can find that 80a+8b = 428
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Let's calculate the values of p ( 7 ) and p ( 3 ) :
p ( 7 ) = 7 2 a + 7 b + c = 4 9 a + 7 b + c
p ( 3 ) = 3 2 a + 3 b + c = 9 a + 3 b + c
Subtracting, we have p ( 7 ) − p ( 3 ) = 4 9 a + 7 b + c − 9 a − 3 b − c = 4 0 a + 4 b
Try subtracting p ( 9 ) − p ( 1 ) too: p ( 9 ) − p ( 1 ) = 8 1 a + 9 b + c − a − b − c = 8 0 a + 8 b
This is getting us nowhere, right? Look again at the two values. Notice that 2 ( 4 0 a + 4 b ) = 8 0 a + 8 b , so the value of p ( 9 ) − p ( 1 ) is double the value of p ( 7 ) − p ( 3 ) .
Substititing, we have p ( 9 ) − p ( 1 ) = 2 ⋅ 2 1 4 = 4 2 8