Quadratic Formula Worksheet With Answer Key - Tutoring And Learning Centre, George Brown College, 2014 Page 3
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4Quadratic Formula
Example 3:
2
Use the quadratic formula to find the x-intercept(s) of y = 4x
–36x + 81.
Step 1: Determine the values of a, b and c.
From the equation, a = 4 ; b = –36 and
−(– 36) ± �(– 36)
− 4(4)(81)
2
x =
c = 81
2(4)
Step 2: Plug in the values for a, b and c
into the quadratic formula.
36 ± √ 0
x =
8
Step 3: Simplify and solve.
x = 4.5
Step 4: State the final answer.
Therefore, there is one x-intercept which
is (4.5, 0).
Practice Questions:
1. Solve using the quadratic formula. Round to 2 decimal places, if necessary.
2
a) 0 = 4x
+ 8x + 2
−4x −3
2
b) 0 = 2x
2
c) 9x
+ 12x + 4 = 0
2
d) 3x
+ 4x + 2 = 0
e) −6x
2
+ 18x = 1
f) x(x−2) = 4
2. Find the x-intercept(s) of each quadratic relation (if any) using the quadratic
formula.
2
a) y = 2x
+ 14x + 24.5
2
b) y = x
+ 1
+ 2x −3
2
c) y = 7x
Answers:
= −1.71
= −0.29
2. a) (−3.5, 0)
1. a) x
x
1
2
= −0.58
b) x
x
= 2.58
b) no x-intercepts
1
2
c) x = −0.67
c) (−0.81, 0) and (0.53, 0)
d) no real solutions
e) x
= 0.06
x
= 2.94
1
2
= −1.24
f) x
x
= 3.24
1
2
Tutoring and Learning Centre, George Brown College 2014
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