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Core 3: differentiating exponentials and logs (help thanks!)

hi everyone, I am having some trouble with this question, I just cant get to the answer they have got :frown:

thanks for any help!

12c) use intergration to show that the intergral from a to 0

(2 - e^-x - x)dx is equal to 1 + a - 1/2 a^2

i got:

[2x + e^-x - x^2/2] a,0

which goes to:

2a + e^-a - a^2/2 -1

how that equals 1 + a - 1/2 a^2 i dont know?

thanks again!

byeee

Reply 1

Adam92

Ammar21

hi everyone, I am having some trouble with this question, I just cant get to the answer they have got :frown:

thanks for any help!

12c) use intergration to show that the intergral from a to 0

(2x - e^-x - x)dx is equal to 1 + a - 1/2 a^2

i got:

[2x + e^-x- x^2/2] a,0

which goes to:

2a - e^-a - a^2/2 -1

how that equals 1 + a - 1/2 a^2 i dont know?

thanks again!

byeee

That bit's wrong. What's the integral of 2x?

Reply 2

JAKstriked

The integral of

-e^{-x}

e^{-x}

so that bit is right. The 2x is not.

Reply 3

Ammar21

sorry guys typing error - good spot tho!! - ill edit!

Reply 4

Ammar21

sorry guys typing error - good spot tho!! - ill edit!

lol typing error (im retarted!)

Reply 5

Adam92

Ammar21

hi everyone, I am having some trouble with this question, I just cant get to the answer they have got :frown:

thanks for any help!

12c) use intergration to show that the intergral from a to 0

(2 - e^-x - x)dx is equal to 1 + a - 1/2 a^2

i got:

[2x + e^-x - x^2/2] a,0

which goes to:

2a - e^-a - a^2/2 -1

how that equals 1 + a - 1/2 a^2 i dont know?

thanks again!

byeee

Right, edited post.

That bit's wrong also.

Reply 6

Ammar21