Question 182245This question is from textbook algebra II
:
x2 + 9x = -20
This question is from textbook algebra II
Answer by mastermath(14)   (Show Source):
You can put this solution on YOUR website! x²+ 9x = -20
First, add 20 on both the sides
x²+ 9x + 20 = -20 + 20
x²+ 9x + 20 = 0
Now split 9x as sum of 4x and 5x
x²+ 4x + 5x +20=0
Now, take x common from the first two terms.
And take 5 common from the next two terms.
x(x+4)+5(x+4)=0
(x+4)(x+5)=0
Using the zero-product rule
If the product of two numbers is 0, then either of the numbers is 0
so, (x+4)=0 or (x+5)=0
thus, x=-4 or x=-5
Ans: x=-4,-5
Proof:
Put x=-4 in the equation
x²+ 9x= (-4)²+9(-4) = 16 - 36 = -20
now put x=-5 in the equation
x²+ 9x= (-5)²+9(-5) = 25 - 45 = -20
Thus, both the values are satisfied.
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