$$12 + 12+(y*y*y) = 51$$ I tried working this out and I got that $y = 9$ using that answer I had to figure out what z is equal to $z + z +(z * y) = 25$. Im struggling in working this out, was my answer my the previous question wrong (y) ?
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1$\begingroup$ Where did the $z$ come from? I don't see any $z$'s in the original equation ... $\endgroup$– Matti P.Commented Jan 27, 2021 at 14:11
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$\begingroup$ $12+12+(y\cdot y\cdot y)=51$. We subtract $12$ from both sides twice so we only have the unknown variables on the left and known numbers on the right. This leaves us with $y\cdot y\cdot y = 27$, or written differently $y^3=27$. Now... what number when cubed is equal to $27$? Note the difference between the statement $3y=27$ and the statement $y^3=27$. You seem to have added the $y$'s together instead of multiplying them, that or misunderstand how to reduce exponents. $\endgroup$– JMoravitzCommented Jan 27, 2021 at 14:12
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$\begingroup$ Are you using $*$ to denote multiplication? $\endgroup$– The PointerCommented Jan 27, 2021 at 14:12
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$\begingroup$ We are trying to find out what number z is $\endgroup$– charCommented Jan 27, 2021 at 14:13
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$\begingroup$ Yes, and we'll get to $z$ after we finish correctly figuring out what $y$ is. @MattiP. it appears to be a system of equations (i.e. a multipart question) where the first equation given was enough to solve for $y$ and we try to use the result in the second equation to further figure out what $z$ is. $\endgroup$– JMoravitzCommented Jan 27, 2021 at 14:14
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1 Answer
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$$12+12+(y\cdot y\cdot y)=51$$
Subtract $12$ from each side twice
$$y\cdot y\cdot y = 27$$
Simplify as an exponent for my own sanity...
$$y^3=27$$
Note that this is $y\cdot y\cdot y = y^3$, not $y+y+y=3y$. Perhaps you got addition and multiplication mixed up?
From here, we can take the cubic root of each side:
$$\sqrt[3]{y^3}=\sqrt[3]{27}$$
This simplifies, the cubic root of a (real) number cubed is the original number, $\sqrt[3]{y^3}=y$. As for the cubic root of $27$, well, you can use a calculator for that or you can recognize the cubic roots of several small examples. You should hopefully be able to recognize $1^3=1, 2^3=8, 3^3=27, 4^3=64, 5^3=125$ at a minimum since these numbers occur so frequently. The cubic root of $27$ then is the number who when cubed is equal to $27$ and is then $3$.
$$y = 3$$
answered Jan 27, 2021 at 14:21