Question

If f(x)=-x2(power of ) -5x+18, what is f(-5) a.18 b.68 c. -18 d. -68 e. none of these

Answer 1

As

• 
  `f(-5)=18`

Hence, the option 'a' is true.

Explanation:

Given the expression

`f\left(x\right)=-x^2-5x+18`

Putting x = -5 in the expression

`f\left(-5\right)=-\left(-5\right)^2-5\left(-5\right)+18`

`=-\left(-5\right)^2+5\cdot \:5+18`

`=-5^2+5\cdot \:5+18`

`=-5^2+25+18`

`=43-5^2`

`=43-25`

`=18`

Therefore,

• 
  `f(-5)=18`

Hence, the option 'a' is true.