Start by identifying the values of a, b, and c. Make sure that all of the terms are on the same side and in the correct order for the standard form of a quadratic function.
3/2 and 5
Practice makes perfect
To solve the given equation by factoring, we will start by identifying the values of a, b, and c.
- 2x^2+13x=15 ⇔ - 2x^2+ 13x+( - 15)=0
We have a quadratic equation with a= - 2, b= 13, and c= - 15. To factor the left-hand side, we need to find a factor pair of -2 * ( - 15)=30 whose sum is 13. Since 30 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 of Factors
Sum of Factors
- 1 and - 30
^(- 1* (- 30)) 30
- 1+(- 30) - 31
1 and 30
^(1* 30) 30
1+30 31
- 2 and - 15
^(- 2* (- 15)) 30
- 2+(- 15) - 17
2 and 15
^(2* 15) 30
2+15 17
- 3 and - 10
^(- 3* (- 10)) 30
- 3+(- 10) - 13
3 and 10
^(3* 10) 30
3+10 13
-5 and - 6
^(-5* (- 6)) 30
-5+(- 6) - 11
5 and 6
^(5* 6) 30
5+6 11
The integers whose product is 30 and whose sum is 13 are 3 and 10. With this information, we can rewrite the linear factor on the left-hand side of the equation, and factor by grouping.
We found that the solutions to the given equation are x= 32 and x=5. To check our answer, we will graph the related function, y=- 2x^2+13x-15, using a calculator.
We can see that the x-intercepts are 32 and 5. Therefore, our solutions are correct.
