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what two numbers multiply to give 324 but add to make -77?

 Jun 15, 2016
 #1
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what two numbers multiply to give 324 but add to make -77?

 

 

a * b =324, a+b=-77, solve for a,b

 

a=-4.46693

b=-72.53317

 Jun 15, 2016
 #2
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I think your teacher or your book expected two simple whole integers, which are:

 

-81 x 4 = - 324

-81 + 4=-77

But it doesn't work for 324 because it gives a negative answer. Unless you made a mistake?.

 Jun 15, 2016
 #3
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\(x\times y=324\)

\(x+y=-77\)

 

There are several ways to solve this problem.  I will solve this problem this way,

 

Solve for x in the first equation

 

\(x\times y=324\)

 

\(x\times \frac{y}{y}=\frac{324}{y}\)

 

\(x\times 1=\frac{324}{y}\)

 

\(x=\frac{324}{y}\)

 

Subsitute \(\frac{324}{y}\) for x in the second equations and solve for y.

 

\(\frac{334}{y}+y=-77\)

 

\(\frac{334}{y}\times y+y\times y=-77\times y\)

 

\(\frac{334\times y}{y}+y\times y=-77\times y\)

 

\(334+y\times y=-77\times y\)

 

\(334+y^2=-77\times y\)

 

\(334+y^2=-77y\)

 

\(334+y^2+77y=-77y+77y\)

 

\(334+y^2+77y=0\)

 

\(y^2+77y+334=0\)

 

\(y^2+77y+334-334=0-334\)

 

\(y^2+77y+0=0-334\)

 

\(y^2+77y+0=-334\)

 

\(y^2+77y+0+1482.25 =-334+ 1482.25\)

 

\(y^2+77y+1482.25 =-334+ 1482.25\)

 

\(y^2+77y+1482.25 = 1148.25\)

 

\((y+ 38.5 )^2= 1148.25\)

 

\((\sqrt{y+ 38.5})^2=\sqrt{1148.25}\)

 

\(y+ 38.5=±\sqrt{1148.25}\)

 

\(y+ 38.5≈±\ 33.8858377497148505\)

 

\(y+ 38.5≈ 33.8858377497148505\) and \(y+ 38.5≈- 33.8858377497148505\)

 

\(y+ 38.5-38.5≈ 33.8858377497148505-38.5\)and \(y+ 38.5-38.5≈ -33.8858377497148505-38.5\)

 

\(y+ 0≈ 33.8858377497148505-38.5\) and \(y+ 0≈ -33.8858377497148505-38.5\)

 

\(y≈ 33.8858377497148505-38.5\) and \(y≈ -33.8858377497148505-38.5\)

 

\(y≈-4.6141622502851495\) and \(y≈-72.3858377497148505\)

 

Subsitute y in the second equation and solve for x.

 

\(x+(-4.6141622502851495)≈-77\) and \(x+(-72.3858377497148505)≈-77\)

 

\(x-4.6141622502851495≈-77\) and \(x-72.3858377497148505≈-77\)

 

\(x-4.6141622502851495+4.6141622502851495≈-77+4.6141622502851495\) and \(x-72.3858377497148505+72.3858377497148505≈-77+72.3858377497148505\)

 

\(x-0≈-77+4.6141622502851495\) and \(x-0≈-77+72.3858377497148505\)

 

\(x≈-77+4.6141622502851495\) and \(x≈-77+72.3858377497148505\)

 

\(x≈-72.3858377497148505\) and \(x≈-4.6141622502851495\)

 Jun 17, 2016

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