anonymous
  • anonymous
Algebraic expressions.. Evaluate 3x-y2 for x = -3/4 and y = -2/5
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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welshfella
  • welshfella
you replace x by -3/4 and y by -2/5 in the expression and work it out. = 3*(-3/4) - (-2/5)^2
anonymous
  • anonymous
I know i plug it it in so it would be 3(-3/4) - (-2/5)^2 right?
welshfella
  • welshfella
yes

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anonymous
  • anonymous
i dont like working with fractions i always get confused
welshfella
  • welshfella
multiplying fractions is not too difficult just multiply top and bottom:- |dw:1440933535144:dw|
welshfella
  • welshfella
* thats 15 not 35!!
anonymous
  • anonymous
is there more steps?
welshfella
  • welshfella
yes do the multiplication and squaring first finally subtract
anonymous
  • anonymous
hmm
welshfella
  • welshfella
|dw:1440933718810:dw|
anonymous
  • anonymous
the first one was just an example right?
welshfella
  • welshfella
yes
anonymous
  • anonymous
ok :)
anonymous
  • anonymous
do i multiply the 4 and -3
anonymous
  • anonymous
and then add the 3
welshfella
  • welshfella
no - multiply the top numbers that is -3 and 3
anonymous
  • anonymous
oh okay!
anonymous
  • anonymous
okay i got 9/4 - 4/25 is it wrong?
welshfella
  • welshfella
no that is correct
anonymous
  • anonymous
and then i subtract?
anonymous
  • anonymous
or multiply
anonymous
  • anonymous
the answer on the worksheet says its -2 41/100|dw:1440934161182:dw|
welshfella
  • welshfella
notice that 9/4 is an improper fraction I ts easier at this stage to convert iutto a mixed number 9 divide by 4 is 2 and there is a remainder 1 so 9/4 = 2 1/4
anonymous
  • anonymous
oh!
welshfella
  • welshfella
so we have |dw:1440934184640:dw|
anonymous
  • anonymous
got it
welshfella
  • welshfella
sorry it was negative -9/4 - 4/25 not 9/4 - 4/25
anonymous
  • anonymous
its okay
welshfella
  • welshfella
now you can only subtract and add fractions withe the same denomiantor so you need to find the LCD (Lowest Common Denominator) of 4 and 25
welshfella
  • welshfella
LCD of 4 and 25 is 100
anonymous
  • anonymous
yes it is
welshfella
  • welshfella
so converting 1/4 to hundredths we multiply the top ond bottom of the fraction by 15 |dw:1440934433350:dw|
anonymous
  • anonymous
does the 2 dissapear?
welshfella
  • welshfella
and |dw:1440934510629:dw|
welshfella
  • welshfella
No we'll bring that in at the end
welshfella
  • welshfella
so we have now got |dw:1440934591025:dw|
anonymous
  • anonymous
OH!! I understand now :) thanks so much!
welshfella
  • welshfella
good Try and practice some more problems of same type and you'll gain confidence
welshfella
  • welshfella
fractions are a bit tricky
anonymous
  • anonymous
yes i will thank you!
welshfella
  • welshfella
yw
anonymous
  • anonymous
okay i just tried figuring out how to get 41 do you subtract the 25 and 10?
welshfella
  • welshfella
- and watch the negatives - i forgot them a few times myself!
welshfella
  • welshfella
no -16 - 25 = -41
anonymous
  • anonymous
you add 2 to 25 and add 2 to 10? and that gives you 39? and -2 + 41 = 39
anonymous
  • anonymous
oh
anonymous
  • anonymous
i thought that was a 10 sorry
welshfella
  • welshfella
you are really adding negative numbers -16 + (-25) = -41 Tha'ts what makes this one extra tricky - you have negatives and fractions..
welshfella
  • welshfella
- thats my bad drawing
anonymous
  • anonymous
Okay i just checked my work :)
welshfella
  • welshfella
lets try -3/16 - 7 / 16 what does that equal?
welshfella
  • welshfella
-3 - 7 = ?
anonymous
  • anonymous
-10?
welshfella
  • welshfella
yea so its -10/16 when add/subtract the denominator stays the same
anonymous
  • anonymous
yeah i always get confused by negatives
welshfella
  • welshfella
Practice
anonymous
  • anonymous
Thanks again :)

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