# Given f(x) = 4x + 5 and h(x) = sqrt(5x - 4) how do you find (hf)(4)?

Jul 27, 2018

$\left(h f\right) \left(4\right) = \sqrt{101}$

#### Explanation:

$f \left(x\right) = 4 x + 5 , h \left(x\right) = \sqrt{5 x - 4}$

$\left(h f\right) \left(x\right) = h \left(f \left(x\right)\right) = h \left(4 x + 5\right) = \sqrt{5 \left(4 x + 5\right) - 4}$

$\left(h f\right) \left(4\right) = \sqrt{5 \left(4 \cdot 4 + 5\right) - 4} = \sqrt{105 - 4} = \sqrt{101}$

$\therefore \left(h f\right) \left(4\right) = \sqrt{101}$ [Ans]