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Teachers' Lounge Discussion: System of equations

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From: Loyd

To: Teacher2Teacher Public Discussion
Date: 2002102608:26:48
Subject: Re: Re: math system of equations

On 2002102607:25:12, N.Goodluck Nwaerondu wrote: >On 2002102112:56:59, megan wrote: >> please help me solve this system of equations. >>y=3/5x-2 >>y=x/10+1 >>y=y >therefore: 3/5x-2=x/11 OR did you mean x/10x+1 >then cross multiply: >3(10x+1) = x(5x-2) OR 3(11) = x(5x-2) >5x^2-32x-3 = 0 5x^2-2x-33=0 >Then use the quadratic formula to solve: N.Goodluck I think the poster (who didn't use grouping symbols) meant the following: y=(3/5)x-2 y=(x/10)+1 That is, the x in eq 1 is in the numerator and the 10 in equation 2 is in the denominator. I often see these confusions which grouping symbols would clear up. I think it is clearer if it was written using the three line method vice the one line typewriter method: y = 3x -2 --- 5 y = x + 1 -- 10 These are equations in the y=mx+b format where the slope is 3/5 in the first one and 1/10 in the second one. That is why, I recommend using grouping symbols to avoid confusion. When using a pencil, most students and teachers get it right. 3x -2 = x + 1 -- -- 5 10 Multiply through by 10: 6x - 20 = x + 10 5x = 30 x =6 By substitution, we find that y = 1.6 or 8/5.

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