Dan has £100. Colin takes £y. How much is left
2 answers:
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Answer:
C, A, A
Step-by-step explanation:
In general, you ...
- identify the coefficients of one of the variables
- swap them, and negate one of them
- multiply the corresponding equations by the "adjusted" coefficients.
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In problem 1, the x-coefficients are 8 and 2. A common factor of 2 can be removed so that we're dealing with the numbers 4 and 1. Assuming we want to multiply one of the equations by 1, leaving it unchanged, the value we want to multiply by will be -4. After we swap the coefficients, that multiplier is associated with equation 2:
multiply equation 2 by -4 . . . (eliminates x)
Likewise, the y-coefficients in problem 1 are -1 and 3. Again, if we want to multiply one of the equations by 1, leaving it unchanged, the coefficient we will change the sign of is -1 (becomes 1). After we swap the coefficients, the multiplier 3 is associated with equation 1:
multiply equation 1 by 3 . . . (eliminates y)
These two choices are B and A, respectively, so the one that does NOT work for problem 1 is choice C, as indicated below.
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The other problems are worked in a similar fashion.
