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Question
solve using substitution x-2y=1 3x+3y=21
Hi Maddie
Do you have any example given in your textbook?
Step 1: Make either "x" or "y" the subject of an equation.
e.g., with x-2y=1, we can add 2y to both sides. This gives x=2y+1 ...call this equation [#1].
Our goal is to eliminate "x", for the time being, in order to find the value of the unknown "y".
We do this by making the substitution x=2y+1 (from equation [#1]) into 3x+3y=21.
This gives 3*(2y+1)+3y = 21
6y+3+3y = 21
9y = 21-3
y = 18/9 = 2.
Now, put y=2 into [#1]. We get x=2*2+1, i.e., x=5.
Solution: x=5 and y=2.
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Josh
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When I work through problems, I like to emphasize concepts which I believe are worth noting. I will try to answer questions in the following areas, but not at the advanced level. Algebra. Sequences & Series. Trigonometry. Functions & Graphs. Coordinate Geometry. Quadratic Polynomials. Exponential & Logarithms. Basic Calculus. Probability, Permutation and Combination. Mathematical Induction. Complex numbers. Physics problems.
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