MC Q20 Solution?

[qshyrn]

MC Q20 from memory:
int(f(x),x,0,a)=a     F(a)-F(0)=a

2*int(f(x/5)+3,x,0,5a)=??

my working out:
= 2 int(f(x/5),x,0,5a) + 6*int(1,x,0,5a)
= 2 (F(a)-F(0)) +30a
= 2a+30a
=32a

but this wasnt one of the options.... 

[Stormer]

40a is what I got. First one is 10a?

[Linkage1992]

I got 32 too. So i just thought stuff it and put the one that had 40.

[fady_22]

I used the substitution method as in spesh (which meant that the first integral was multiplied by 5). And I got 40a too.

[taiga]

i just put 40

[Linkage1992]

I hope you're all right. Guesses FTW

[pirocan1]

it had to be larger than 30a so it was either D or E.

Fortunately, I guessed the right one.

[vea]

I got 32a at first but then somehow got 40a.

[Stroodle]

i just put 40

rofl, me too. had to be above thirty, and that first term was looking really 10ish to me.

[samiira]

i did that ini mini maini mo thing on that question and it turned out right

[goshipeoyo]

I used the substitution method as in spesh (which meant that the first integral was multiplied by 5). And I got 40a too.

You dont need spesh to do it? Haha
Once you separate the integrals it works out to be 10a + 30a because int(f(x/5),x,0,5a) =2*5F(a) = 10a, etc

[taiga]

i just put 40

rofl, me too. had to be above thirty, and that first term was looking really 10ish to me.

yeah same i just calculated the other one, and was like, yeah about five times something equals 10, probs not 20 thats too big. so probably a 10+20

[whyareyoureadingthis]

Yeah I got 32 and put 40.

[mmmmm]

I hope you're all right. Guesses FTW

+1
HI FIVE!!

Also half guessed the last one and got it right.

[pirocan1]

another case of vcaa fail.