further exponentials help 2 Watch

panjabiflower
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#1
Report Thread starter 10 years ago
#1
how would i work out these two q's

1) solve as simultaneous equations:
e^y+5-9x=0
y-ln (x+4)=2

2) find as natural logarithms the roots of the equation
2e^x+3e^-x=7
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generalebriety
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#2
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1) Plug y = 2 + ln(x+4) (from the second equation) into the first. Use index rules and the fact that e^(ln P) = P.
2) Multiply through by e^x, and then make the substitution u = e^x (remembering that u^2 = e^2x).
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panjabiflower
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#3
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i still do not understand how to work out no. 1
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generalebriety
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#4
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(Original post by panjabiflower)
i still do not understand how to work out no. 1
Can you post your working, please?
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panjabiflower
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#5
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e^2+ln(x+4) +5-9x=0
don't know how to work this out on calculator...

also for the 2nd q
is this how you work it out
e^2x+ e^-3x=7
e^-6x=7
ln7=1.95
-6x=1.95
x=1.95/-6
=-0.32
not sure if this is right plz help if you can
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Chewwy
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#6
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(Original post by panjabiflower)
e^2+ln(x+4) +5-9x=0
no.
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