Question

pls help!! I shall mark you brainiest!
f(x)=bx^2+5
For the function f defined above, b is a constant and f(−7)=100. Which of the following is equal to the value of f(−2)?

A) f(1)
B) f(2)
C) f(0)
D) f(−1)

Answer 1

Answer:

(B) is the answer.

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Method 1

Let's not solve for b.

We know $f(x)$ is a quadratic function.

It's symmetric from line $x=0$.

$f(-2)=4b+5$

$f(2)=4b+5$

∴ $f(-2)=f(2)$

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Method 2

Let's solve for b.

We know :

*$f(x)=bx^2+5$.

*$f(-7)=100$

As the function is defined, substitute $x=-7$ into the function.

→ $f(-7)=49b+5$

→ $f(-7)=100$

→ $49b+5=100$

→ $49b=95$

∴ $b=\frac{95}{49}$

But we don't need the b anyways.

Is it helpful?

Answer 2

Hola mate

Here is your answer -

B) f(2)

Explanation:

We know f(x) is a quadratic function.

It's symmetric from line x = 0.

f(-2) = 4b + 5

f(2) = 4b + 5

f(-2) = f(2)