(i) Solve the equation 2X² - 11x - 21 = 0.
(ii) Hence, solve the equation
2(y + 2)² - 11(y + 2) - 21 = 0.
please can someone help me understand the relation between these two questions and can you help me asnwer them.
help would be really appreciated.
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Answers
Answered by
0
Step-by-step explanation:
Alex Boroda
May 17, 2015
2
x
2
−
11
x
−
21
can be factored as
(
x
−
7
)
(
2
x
+
3
)
, as follows:
2
x
2
−
11
x
−
21
=
2
x
2
−
14
x
+
3
x
−
21
=
(
2
x
2
−
14
x
)
+
(
3
x
−
21
)
=
2
x
(
x
−
7
)
+
3
(
x
−
7
)
=
(
x
−
7
)
(
2
x
+
3
)
Answered by
3
Answer:
(i) x=7 or -3/2
(ii) y=5 or -7/2
Step-by-step explanation:
(i) 2x² - 11x - 21 = 0
2x² - 14x+3x - 21 = 0
2x(x-7)+3(x-7)=0
(x-7)(2x+3)=0
so x=7 or -3/2
------------------------------------
(ii)2(y + 2)² - 11(y + 2) - 21 = 0
Let y+2=x
then the eqn becomes
2x² - 11x - 21 = 0
From above solution
x=7 or -3/2
So Case I
If x=7
then y+2=7, y=7-2=5
Case II
If x=-3/2
then y+2=-3/2
y=-2-3/2=-7/2
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