find the roots of the following quadratic equations if they exist by the method of completing square. (i) x^2 - 6x - 27 = 0 (i) 4t^2 - 8t+ 3 = 0
Answers
(i) x²-6x-27=0
=> x²-9x+3x-27=0
=> x(x-9)+3(x-9)=0
=> (x+3)(x-9)=0
=> x+3=0 or x-9=0
x= -3 or x= 9
Ignore negative value
Hence, x=9
(ii) 4t²-8t+3=0
=> 4t²-6t-2t+3=0
=> 2t(2t-3)-1(2t+3)=0
=> (2t-1)(2t+3)=0
2t-1=0 or 2t+3=0
2t=1 or 2t=-3
t=1/2 or t=-3/2
Ignore negative value
Hence, t=1/2
Answer:
(i) x²-6x-27=0
(i) x²-6x-27=0=> x²-9x+3x-27=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative value
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=02t-1=0 or 2t+3=0
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=02t-1=0 or 2t+3=02t=1 or 2t=-3
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=02t-1=0 or 2t+3=02t=1 or 2t=-3t=1/2 or t=-3/2
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=02t-1=0 or 2t+3=02t=1 or 2t=-3t=1/2 or t=-3/2Ignore negative value
(i) x²-6x-27=0=> x²-9x+3x-27=0=> x(x-9)+3(x-9)=0=> (x+3)(x-9)=0=> x+3=0 or x-9=0x= -3 or x= 9Ignore negative valueHence, x=9(ii) 4t²-8t+3=0=> 4t²-6t-2t+3=0=> 2t(2t-3)-1(2t+3)=0=> (2t-1)(2t+3)=02t-1=0 or 2t+3=02t=1 or 2t=-3t=1/2 or t=-3/2Ignore negative valueHence, t=1/2
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