Question

I need help on number 16 these instructions say to solve these equations by cross multiplying

Answer 1

15. x = 4

16. a = 19

Explanation:

"Cross multiply" essentially means "multiply both sides of the equation by the product of the denominators."

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15.

`(x)/(6)=(2)/(3)\\\\3(x)=6(2)\qquad\text{`

This is an example of a problem in which cross-multiplying introduces the need for an extra step: divide by 3. Had we simply multiplied by the denominator of the x-term, we would have been finished in one step:

x = 6(2/3) = 4

That is, rather than multiplying by the product of the denominators, sometimes the problem can be solved more easily if you multiply by their least common multiple.

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16.

`(a+1)/(a+5)=(a-4)/(a-1)\\\\(a-1)(a+1)=(a+5)(a-4)\qquad\text{`