who can help me in these questions !

Question 10: Note that since the lines are parallel, their slopes must be the same [and negative since the line is going downward] and they also differ in their y-intercepts [one + and one -] as well based on the graph. 

D does have the same slope, but notice that both y-intercepts are positive...the graph has 1 equation that has a negative y-intercept.

C also has one that is x -y which means the x would become positive again once it is moved to the other side...while the other equation still has a negative x...

A has x, 2x, and 2y, so notice that the slopes would dramatically differ...

Only B makes sense since you notice that x + y = # andx + y = -#...the slopes are equal and the #'s are opposite signs.

Question 16: y is definitely greater than 0...but notice that is restricted to a maximum of y = 3. Only choice C makes sense.

Question 19: On the graph, when x = 1 when y = 0.

y = -ln x --> 0 = - ln(1)...Yes!

y = e^-x --> 0 = e^(-1)...No!

y = e^x --> 0 = e^1...No!

y = ln x --> 0 = ln 1...Yes!

Now, notice that if we took ln(0.9) we would get -0.1053605156578263...and this graph is in the positive range when x <1...so, -lnx would make it positive...A.

I'm going to do the last one  

$$y=\sqrt{25-x^2}\\
when\; x=4\\
y=\sqrt{25-16}=\sqrt9=3$$

So you have a rectangle with length 2 units and height 3 units.

So the area is 2*3=6u^2

verrrry niiiice ... 

I understand all question 

thank you melody and aziz