Hi my name is patty and I am a student taking a pre-calculus course and need help with the following:

5x - 4y = 13

2y + 3x = -1

Would I solve like this,

2y +3x = -1

y = -1/2 -3/2 x

solve for x

5x - 4(-1 -3x) = 13 now I need help ?

Thank you, Patty.



Hi Patty,

What you have is almost correct, there is however an error in the last line. When you substituted y = -1/2 -3/2 x you should have gotten

5x - 4(-1/2 -3/2 x) = 13

The next step is to multiply through the expression in parenthes by -4 to get

- 4(-1/2 -3/2 x) = 2 + 6 x Thus 5x - 4(-1/2 -3/2 x) = 13 becomes 5x + 2 + 6x = 13 Subtract 2 from each side to get 11 x = 11 and hence x = 1.

Now use y = -1/2 -3/2 x to find y and finally substitute the values of x and y into the two original equations to verify your result.

Penny

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