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1.05 Solving quadratic equations

Worksheet
Solving equations algebraically
1

A monic quadratic equation has solutions x = \pm 5. What was the equation?

2

Solve the following equations:

a
x^{2} = 11
b

x^{2} = 25

c

x^{2} - 25 = 0

d
x^{2} = 98
e

\dfrac{x^{2}}{25} - 3 = 6

f

\left(x - 7\right)^{2} = 81

g

\left(7 - x\right)^{2} = 81

h

\left( 4 x + 3\right)^{2} = 64

i

\left(x - 4\right)^{2} = 10

j
25 y^{2} = 36
k
5 \left(p^{2} - 3\right) = 705
l
\left( 4 x - 9\right)^{2} = 0
3

How many real solutions does the equation x^{2} + 64 = 0 have?

Solving equations by factorisation
4

Solve the following equations:

a

- 3 m \left(m + 2\right) = 0

b

\dfrac{m}{6} \left(m - 10\right) = 0

c
x \left(x + 6\right) = 0
d

\left(x - 7\right) \left(x - 6\right) = 0

e

\left( 4 x - 17\right) \left( 3 x + 11\right) = 0

f

x^{2} + 19 x + 90 = 0

g

x^{2} + 6 x - 55 = 0

h

x^{2} - 17 x + 72 = 0

i

x^{2} - 5 x - 14 = 0

j

- x^{2} + x + 20 = 0

k

\dfrac{x^{2} - 5 x}{8} = 3

l
- 8 x + x^{2} = - 6 - x - x^{2}
m

3 y - 15 y^{2} = 0

n

x^{2} - 64 = 0

o
m^{2} = 14 m
p

m^{2} = m + 20

q

4 x^{2} + 8 x - 32 = 0

r

x^{2} - 20 x + 100 = 0

s

x \left(x + 2\right) = 48

5

Solve the following equations:

a

x - \dfrac{45}{x} = 4

b

\left(y + 1\right)^{2} = 4 y + 4

c

\left( 5 x^{2} + 13 x + 6\right) \left( 2 x^{2} + 13 x + 20\right) = 0

d

\dfrac{12 + 11 x}{5 x} = x

e

\dfrac{x + 1}{2} - \dfrac{x + 2}{3} = \dfrac{1 - x}{3 x + 1}

f

\dfrac{7}{x \left(x + 3\right)} + 5 = \dfrac{x + 4}{x}

g
5 x^{2} + 22 x + 8 = 0
h
x^{2} + 12 x = 0
6

Write down a monic quadratic equation that has two solutions, 7 and - 4. Write the equation in factorised form.

7

Form a monic quadratic equation which has solutions x = - 3 and x = - 5. Write the equation in expanded form.

Complete the square
8

Consider the equation x^{2} - 3 x = 6. What should be added to both sides of the equation in order to complete the square?

9

For each equation below, complete the square by completing each statement:

a

x^{2} + 4 x + ⬚ = \left(x + ⬚\right)^{2}

b

x^{2}-⬚x+16 = \left(x - ⬚\right)^{2}

c

x^{2}-\dfrac{7}{4}x+⬚= (x-⬚)^2

10

Solve the following by completing the square. Leave your answer in simplified surd form where necessary.

a

x^{2} - 6 x - 16 = 0

b

x^{2} + 5 x + 6 = 0

c

2 x^{2} - 20 x - 32 = 0

d

x^{2} + 18 x + 32 = 0

e
x^2+8x - 9=0
f
x^2-10x+1=0
g
x^2 +6x - 11=0
h
3x^2-18x+9=0
Quadratic formula
11

Solve the following equations by using the quadratic formula:

a

x^{2} + 11 x + 28 = 0

b

x^{2} - 5 x + 6 = 0

c

4 x^{2} + 6 x + 2 = 0

d

- 10 + 23 x + 5 x^{2} = 0

e

x^{2} - 5 x + \dfrac{9}{4} = 0

f

- 6 - 13 x + 5 x^{2} = 0

g
2x^2 + 6x - 8=0
h
4x^2 - 10x +4=0
12

Solve the following equations, leaving your answer in surd form:

a

4 x^{2} - x - 10 = 0

b

- 2 x^{2} - 15 x - 4 = 0

c

\dfrac{3 x + 1}{3 x - 1} - \dfrac{3 x - 1}{3 x + 1} = 5

d
3x^2 + 9x - 4=0
13

Solve 3 x \left(x + 4\right) = - 3 x + 4, giving your answers to 2 decimal places.

14

Use the quadratic formula to solve 5 x^{2} + 9 x + 2 = 0. Round your answers to the nearest thousandth.

Mixed equations
15

Solve the following equations:

a

\left(3 - 3 x\right)^{2} = 0

b

x^{2} + 12 x = 0

c

4 y - 24 y^{2} = 0

d
x^2+7x+13=0
e
-x^2-3x-5=0
f
4x^2+20x+25=0
g

y^{2} = 20 y

h

x^{2} = x + 12

i

m^{2} - 27 m = - 182

j

\dfrac{x^{2} - 4 x}{2} = 16

k

\left(y + 1\right)^{2} = 4 y + 4

l

- 4 x^{2} + 25 x - 36 = 0

m

4 x^{2} + 17 x + 15 = 0

n
2x^2-6x+5=0
o
-2x^2+3x-2=0
16

Solve the following equations:

a

4 x^{2} - 7 x - 15 = 0

b
x^2+8x+16=0
c
x^2+12x+36=0
d
x^2-4x+4=0
e
x^2-10x+25=0
f

5 x^{2} + 14 x + 8 = 0

g

4 x^{2} - 17 x + 15 = 0

h

3 x^{2} - 7 x - 20 = 0

i

\dfrac{2 x^{2} - 19 x}{3} = 20

j
15 - 11 b - 12 b^{2} = 0
k
6 k^{2} = - 7 + 13 k
l
4x^2-28x+49=0
m
16x^2-24x+9=0
n
64x^2+16x+1=0
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MA11-1

uses algebraic and graphical techniques to solve, and where appropriate, compare alternative solutions to problems

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