McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
6. Solving x^2+bx+c=0
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Exercise 4 Page 49

Start by identifying the values of a, b, and c.

(m-5)(m-10)

Practice makes perfect

To factor the quadratic expression, we will start by identifying the values of a, b, and c. m^2-15m+50 ⇕ 1m^2+( - 15)m+ 50 For our expression, we have that a= 1, b= - 15, and c= 50. To factor a quadratic expression with leading coefficient a= 1, we need to find two factors of c= 50 whose sum is b= - 15. Since 50 is a positive number, we will only consider factors with the same sign — both positive or both negative — so that their product is positive.

Factor Pair Product Sum
1 and 50 ^(1* 50) 50 1+50 51
- 1 and - 50 ^(- 1* (- 50)) 50 ^(- 1+(- 50)) - 51
2 and 25 ^(2* 25) 50 ^(2+25) 27
- 2 and - 25 ^(- 2* (- 25)) 50 ^(- 2+(- 25)) - 27
5 and 10 ^(5* 10) 50 ^(5+10) 15
- 5 and - 10 ^(- 5* (- 10)) 50 ^(- 5+ (- 10)) - 15

The integers whose product is 50 and whose sum is - 15 are - 5 and -10. m^2-15m+50 ⇔ (m-5)(m-10) Let's use a graphing calculator to confirm our answer. To do so, we will graph the related functions in the same coordinate plane. Note that in the calculator we will use the variable x instead of m.

We see that only one graph appears. This means that both graphs coincide. Therefore, the expression has been factored correctly.