Please help out with these Maths Questions Please answer all

Please help out with these Maths Questions/ Please answer all the questions.

QUESTION 21 Find the value for the function. Find f(x) hen (x) XT 9 I-xl 9 9 9

21) f(x) = |x| +9

find -f(x) = -( |x| +9) = -|x| -9

Option A

25) f(x) = sqrt(9x^2 -7x)

Find f(2x) : plug x = 2x in f(x)

f(2x) = sqrt(9(2x)^2 -7*2x) = sqrt(9*4x^2 -7*2x)

= sqrt(36x^2 -14x)

Option C

27) 5x +3y =80 -----(1)

2x +y =30 ------(2)

Solve by eleimination :

multiply equation 2 by 3: 6x +3y = 180

5x +3y = 80

6x +3y = 90

--------------(subtract)

-x = -180 +80 = -10

x = 10

y = 30 -2x = 30 -2(10) = 10

(x, y) = ( 10,10)