15. f(n)= 2n-3
a) =2(11)-7
=22-7
=15
=2(-6)-7
=-12-7
=-19
b) f(g)=-5x+1
= -5(41)+1
= -205+1
= -204
= -5(-16)+1
= 80+1
= 81
Hello there! The value of x is 20 or -20
"20 or - 20" is one answer so you are supposed to answer 20 or -20, not choose only one.
Step-by-step explanation:

First, we simplify 5² and 4²

Multiply the whole equation by 25 to get rid of the denominator.

Square both sides and solve the equation.

Also don't forget to write "plus or minus" symbol when we are solving a quadratic equation by squaring both sides.

Answer:
49
Step-by-step explanation:
Answer:
x = 1
y = -1
z = 2
Step-by-step explanation:
You have the following system of equations:

First, you can subtract euqation (3) to equation (1):
x + 2y - z = -3
<u>-x +y -z = - 4 </u>
0 3y -2z = -7 (4)
Next, you can multiply equation (3) by 2 and subtract it to equation (2):
2[ x -y + z = 4]
<u> -2x +y -z = -5</u>
0 -y + z= 3 (5)
You multiply equation (5) by 2 and sum (5) with (4):
2[ -y + z = 3]
<u> 3y -2z= -7</u>
y + 0 = -1
Then y = -1
Next, you replace y=-1 in (5) to obtain z:
-(-1) + z = 3
z = 2
Finally, you can replace z and y in the equation (3) to obtain x:
x - (-1) + (2) = 4
x = 1