The equation
∣ x − 1 0 ∣ = 7
is equivalent to the equation
x 2 + a x + b = 0 .
What is the value of a + b ?
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can i know.why must we square the x-10=7?
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We square it to get a quadratic, which is what the question asks for.
|x-10| = 7
tells that x = 3 , x = 17
making it as a quadratic equation
(x - 17) (x - 3) gives
x^2 - 20x + 51
a = -20 b = 51
a+b = 31
Absolute value of (x-10)=7 is also equal to (x-10)^2 = 49. Now the problem can be expanded so x^2-20x+100=49. The equation simplifies to x^2-20x+51. So your a and b are -20 and 51, which gets you answer of 31
|x-10|=7 |17-10|=7 --> 1 solution |3-10|=7 ---> 2 Solution
{Since the next equation is quadratic , we need two solutions}
Substituting , we get 289+17a+b=0 and 9-3a+b=0
Solving them , we arrive at a=-21 and b =50
therefore -21+50 = 31 .
quite easy,,,,, first u had to find out the possible values of x from equation 1 which were - 3 and 17. then , as its given that the equations are equivalent, put the same values of x one by one in equation 2, then u will obtain a pair of linear equations in 2 variables. after solving them the values of a and b come out to be - (-20) and 51 respectively . therefore the answer comes out to be 31
its +3 and 17
Equivalent equations have equivalent roots, so start by finding roots of the first equation. Splitting the absolute value function into separate equations, x − 1 0 = 7 and x − 1 0 = − 7 , so x = 1 7 , 3 . These roots can be expressed as ( x − 1 7 ) = 0 and ( x − 3 ) = 0 . Multiplying together yields ( x − 1 7 ) ( x − 3 ) = 0 , the factored form of a quadratic. The problem asks for coefficients in standard form though, so expanding the latter form yields x 2 − 2 0 x + 5 1 = 0 . The coefficients in question are − 2 0 and 5 1 , so the answer is − 2 0 + 5 1 = 3 1 .
∣ x − 1 0 ∣ = 7 Squaring the equation gets rid of the absolute value, giving: x 2 − 2 0 x + 1 0 0 x 2 − 2 0 x + 5 1 = 4 9 = 0 The sum of the coefficients of the x and constant terms is − 2 0 + 5 1 = 3 1 .
Therefore, the answer is 31 .
from the first equation....x=3,17 substitute x in second equation..... 289 + 17a+b=0 ........(1) 9+3a+b=0.......(2) subtract ....(1) minus (2)....we will get a= -20 substitute a in any one of equation....we will get b = 51 .....so a+b=31
Please write your solutions neatly and use L A T E X . @Harish Kp
Very easy, ∣ x − 1 0 ∣ = 7 has two solution , which is 3 OR 1 7 .
Cause ∣ x − 1 0 ∣ = 7 equivalent x 2 + a x + b = 0 so,
we can substitute x = 3 to x 2 + a x + b = 0 and we got
3 a + b = − 9
now subtitute x = 1 7 , we got
1 7 a + b = − 2 8 9
by system equation two variable , we got
a = − 2 0 , b = 5 1 and the answer is − 2 0 + 5 1 --> 3 1
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The first equation means that x − 1 0 = ± 7 . We can square this equation and keep all solutions: x 2 − 2 0 x + 1 0 0 = 4 9 x 2 − 2 0 x + 5 1 = 0 The answer is − 2 0 + 5 1 = 3 1 .
NOTE: There will be the same number of solutions since an absolute value equation has 2 solutions if the RHS is positive