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alisha [4.7K]
2 years ago
10

How do I solve this?

Mathematics
2 answers:
Elina [12.6K]2 years ago
7 0

Value of xis - 12.

Final Answer is 480

Step-by-step explanation:

Assume that:

First number = x

Second number = 20 - x

Putting the given conditions,

2x^{2} + 3(20 - x)^{2}

Putting the formula (a-b)²=(a²+2ab+b²) in (20-x)²,

2 {x}^{2} + 3(20^{2} - 2 \times 20 \times x +  {x}^{2})

=  > 2 {x}^{2} + 3(400 - 40x + x^{2})

Opening the brackets,

2 {x}^{2} + 3 \times 400 - 3 \times 40x + 3 \times  {x}^{2}

=  > 2 {x}^{2} - 1200 - 120x +  3{x}^{2}

=  > (2x^{2} + 3 {x}^{2}) - 120x + 1200

=  > 5 {x}^{2} - 120x + 1200

As \: x= -  \frac{b}{2a}

=  >  -  \frac{120}{2 \times 5}

=  >  -  \frac{120}{10}

=  >  - 12

Now substituting the value of x in 5x²-120x+1200,

=  > (5 \times {12}^{2} )-(120 \times 12)+1200

=  > (5 \times 144)-(1440)+1200

=  > 720 - 1440 + 1200

=  > 720 - (1440 - 1200)

=  > 720 - 240

=  > 480

mart [117]2 years ago
3 0
X + y = 20 Substitute
x by 2 y - 4 in x + y = 20 to obtain 2 y •
4 + y = 20 Solve for y to find y = 8 and
x = 2y - 4 = 12
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